It looks like Blekko might be including nofollow links if the rel attribute isn't identical to "nofollow", for example on Twitter user profile URLs it's rel="me nofollow". Definitely a bug though.
I've just confirmed the nofollow behavior with Rich at Blekko. Sorry, it does make the results a lot less useful as a guide to what Google's taking into account (along with all the other disclaimers!). I'll be updating the blog post to reflect this.
There are other ways but this makes it easy to see where competitors are being referenced. If you're trying to grow your personal brand, you could see where people you "compete with" are active, and thus put effort towards contributing content to those sources. There's actually a lot you can do with this information. Yeah, and don't discount the power of contributing quality content on different sites like avc.com comments with a consistent username and a link to your personal site in the profile. :)
It includes nofollow links, another problem is that it gives a link in a massive series of links the same weight as others, when Google definitely doesn't. For instance, there is a blog with us in their blogroll hundreds of time, in reality it doesn't do much, they weight it as 90% plus of our juice.
Interesting, certainly not the sites I expected (the place I tested thoroughly and know I get most of my juice from isn't there, but that's all based on anchor text.)