http://www.wordstream.com/link-building Ben Wills and Garrett French are the cofounders of Ontolo, a link building agency . Check out their link building blog  or follow them on Twitter: @benwills  and @GarrettFrench .
(Note: Also check out Ari Ozick's SEO Contrarian  blog for a similar series of interviews with link building gurus Tuesdays of this month.)
What factors go into a "quality" link?
- Backlink profile of prospective linker -- which sites link to the page and the site as a whole
- An engaged, relevant audience
- Distribution and reach of target site -- are they social media participants? Do they have an email newsletter? How far will your link there take you?
- Relevance and value
- Keywords used on page, etc.
- Quantity and quality of backlinks
- Relevance of entire site
- Relevance of entire site's backlinks
Which link building tools do you use every day, paid and/or free?
- Ontolo link prospect data
- BuzzStream 
- Yahoo Site Explorer 
- SEOBook ToolBar 
- My phone
- The public and private ones we've made :)
- Majestic SEO 
If you could build the ultimate link analysis tool, what features would it include?
Garrett: We've built it -- when can we schedule a walkthrough for you? ;)
Ben: A research application that not only gives you data such as PageRank/Authority, titles, etc., like most other apps provide, but makes assessments for how likely the link prospect is to turn into a link.
What are some strategies for brainstorming and creating linkbait?
- Identify SERP dominators  for your target keywords
- Identify media sites that resonate and engage your target market
- Run these sites through YSE to identify their most-linkable pages 
- Note common characteristics of highly linkable content and consider how to work in your company's USPs
- Promote your linkbait by emailing potential linkers 
Ben: Figure out what people want, and give it to them really, really well. Better than anyone else could and better than they could do on their own with a lot of time on their hands.
Some people claim that traditional links are on their way out, due to the spread of social "sharing" via Twitter, Facebook and other social media outlets. Do you think link building will still be important in a year? Five years? How does social media change the link building game?
Garrett: Links remain a core way to share content, no matter what platform you're on. Link building for pure search engine influence may diminish as search engines discover other ways of calculating the value and relevance of content. Link building for market influence -- making sure that your links appear in relevant, offsite content -- will never lose its importance.
Ben: What it comes down to are two factors: Accessing and assessing the value of data quickly (i.e., giving time-value to tweets in the past hour vs. last month), and that the percentage of links and where they appear is constantly shifting.
On the first factor of data access and assessment, right now, no one has access to Facebook's data except for Facebook. Microsoft has Bing; if Microsoft buys Facebook, imagine the new kinds of link algorithms that could be designed by having access to information with timestamps, distribution, comments, "likes," etc. Without a hefty API, Google simply can't access tweets and user relationships fast enough to incorporate time-relevance (imagine tweets appearing in search results similarly to news links). If Google buys Twitter, imagine what they could do with that data.
This leads to the second factor of the "link profile of the internet." What I mean by this is that, currently, X% of links that appear online come from "traditional" means: links pages, articles, directories, blogs, information content, etc. And, let's say that, currently, Y% of links that appear online come from "social networks." (I prefer social networks to social media here, because I consider blogs to be a form of social media, but without user relationships defined, they're not networks. And I think the key question here is about how social networks will impact link valuations.) Obviously, as the use of social networks, like Twitter and Facebook, increases, in order for search engines to continue providing "the most relevant and timely results," they must begin making sense of this data. To answer your question of how it will affect the link building game, I don't think it will change because the nature of link building has always been a constant evolution and change.
Do links to your website from spammy sites or bad neighborhoods negatively impact the your site’s trust or authority with the engines?
Garrett: In my experience, no.
Ben: No. You're only going to be affected by what comes as a result of your actions; i.e., what you link to, etc.
Any tips for marketers embarking on link requests? What tactics get the best response?
Garrett: Know beforehand what motivates the target site owners/operators to link. I wrote an article on link building outreach  and linked to 15+ other resources there.
Ben: Offer money. Seriously. That gets the best response. If you're looking to keep on Google's good side, though (we think it's a good idea), you might be inclined to consider other options.
If I’m going to engage in link buying, what steps should I take to keep from being discovered by Google?
Garrett: Avoid leaving a pattern as much as possible. Use a proxy for negotiating. Get very very paranoid about who you discuss your efforts with and how.
Ben: Think of paid links being discovered in two ways. 1: People reporting you. You'll never be able to fully avoid that. And 2: The patterns that demonstrate that a link has been paid for. Does your link appear near the words "paid links"? "Sponsorships"? "Paid Advertisements"? "Sponsored links"? If it does, that's a red flag. This doesn't mean that Google will believe that it's a paid link, but it might look further or add a little bit to a "link buyer score."
Do you use Toolbar PageRank as a metric for link analysis and research, or do you fall into the camp that it’s merely “green pixie dust” and for “entertainment purposes only”?
Garrett: We have used it, though based on the news it looks like we won't in the future :)
Ben: We use it because it's the only score widely available for intrinsic URL value, it's understood by our clients, and it's at least something to use. Without making your own internet link graph, there's no other way to get at that kind of value. Backlink totals aren't enough ... PageRank is, at least, a pointer.
Do forum signature links, followed blog comment profile links or article directory links pass any value at all, or do you think they’re simply a waste of time for link building?
Garrett: If your target market frequents a given forum then you should be there, with links in sig! Same with blog comments, again if that's where your target market is. Please note that I'm suggesting that you participate to add value to the community, not simply to link drop. As far as general-topic article directories, there are a few decent ones out there, but if you're submitting content look for guest publishing opportunities on relevant blogs or other industry media sites first.
Ben: Again, two things: 1, Google knows it comes from a comment, forum post, etc. They can discount it if they want. 2, People seem to forget the relevance factor ... if there's a forum about Apple products and you sell red iPod Nanos, and you only comment on posts about red iPod Nanos, an assumption can be made ... do you see where this is going?
Which link do you think helps your site more and why: a link from an authoritative, totally unrelated website or a link from a pretty authoritative, highly relevant website? Both are anchor text links, and you have to pick just one.
Garrett: High-relevance, medium-authority website: you will get more leads and clicks from a relevant site, as your link's going to fit more naturally with the content and be relevant to the audience. From a search perspective you're sending a clearer message that the page of your site you're linking to is relevant to the context of the page.
Ben: I'll take a "pretty authoritative" backlink from a relevant website rather than a "highly authoritative" backlink from an irrelevant website. Based on our research for the past two years -- especially in troubleshooting lost rankings -- relevance is much more significant in a backlink profile than value.
Tell us a little bit about the difference in your roles at Ontolo: What types of tasks do you each perform, and how do your respective skill sets complement each other?
Garrett: As the Chief Marketer I handle lead generation, link building with content and software alpha testing. In my client-facing work for Ontolo I handle link prospect qualification, outreach and the creation of linkable content.
I focus on solving narrow, individual problems and fine-tuned details.
Ben: From the conception through startup, my focus has been on figuring out how to create a new process for link prospecting and a new process for link outreach that increases the results of link building efforts. That said, I've been the sole developer of our technology as well as positioned myself in a sales role to communicate the value to prospective clients.
I focus on solving problems of scale and making more sense of more data and patterns.
What this polarity does is to never allow the solution to be fully solved, forcing further innovation. In the end, we continue to bring each other new problems to be solved that the other hasn't considered.
Aside from your own Search Engine Land column, who are some good link building bloggers and writers worth following?
Garrett: I recommend looking at Melanie Nathan's round-up of 18 Must Follow Link Building Experts on Twitter . If you follow all those folks there's pretty much no way that anything about link building can slip past you :) In addition to their Twitter addresses, Ms. Nathan also included their blogs and sites for those who prefer RSS over tweets.
Ben: I don't read too many blogs and I definitely don't read blogs on any sort of regular basis. But, when I have some uncommon programming problems, I have often found solutions on the following two sites. I'll also note that they may not be for the whitest-hat of SEOs: