Links on Twitter are already nofollowed and most are shortened anyway by a shortener. What use can Twiitter be for link building? Link building Eric Ward says the site is perfect for finding niche experts.
It’s not about huge amounts of followers or traffic spikes. You can get that kind of traffic from Digg. But the advantage of Twitter, says Ward, is that people specific to an industry are out there, findable on Twitter.
So if you specialize in little plastic doohickeys they put on shoestrings, irrelevant traffic is not what you’re after. At Search Engine Land, Ward explains how a message that begins as a tweet ends up as a link from a highly trusted website:
A few weeks ago I announced a new site via URLwire, and whenever I do this I set up several alerts/trackers to see where mentions/links show up. I also set up a Twitter search for that new URL....the new site I announced has been tweeted or re-tweeted by seven people…I discovered all of them were health experts in one form or another. Also, all of them had several hundred followers (one had 780), and a quick check of a few dozen of those showed some overlap (expected) as well as frequent health URL tweets. In other words, I’d found a loose community of several thousand collective Twitterer’s who had shared news about a new web site URL.
One of those re-tweets came from a librarian at a med school web site, who did one more thing with that URL. She added a link to it from the med school web site she’s in charge of editing. What started to her as a tweet ended as a permanent link from her high trust web page.
What’s even better about that is that earned link was a free, organic one, the best kind. No manipulation, no buying, no trading. And that one very trusted link is likely to outweigh many links (however they're gotten) from not-so-trusted websites.