Check out the festive cranberries...
My fourpenneth...If one is looking for *influencers* then one must surely track the *influnces*? I might follow Stephen Fry on twitter but if he gives an opinion about Nokia or Microsoft that doesn't mean I'd give the comment any more weight than I would if it came from someone else.
I'd suggest that one crude way to track influence in twitter would be to look at retweets, and as a case study I'd suggest tracking the transmission of Mat's article/meme/retweet.
We can assume that the first person to twitter about this article is you. So from that point in time, who else sent out a tweet with its URL and the abbreviated variations:
http://tinyurl.com/5ruc8d,
bit.ly, budurl, eweri,
hex.io and so on...
By looking at the timing of the postings you can get a reasonable idea of who influenced whom. It's quite likely that there'll be posts made by people completely unconnected within twitter, which would indicate that their influences come from elsewhere.
Also, you may find people who are connected, but in fact their 'influence gradient' (should I trademark that) runs in a counter-intuitive way: for example where an apparent 'follower' posts before the top 50 influencer they're connected to, suggesting that they're picking up on memes outside of twitter, before they're being broadcast by a guru...like Mat.