Anecdotally, Scoble once linked to a blog post of mine in his twitter linkblog and I think I got only two or three clickthroughs from it. So even though he may have 4000 users, measuring the value of a twitter follower is very different from measuring the value of a pageview. What exactly does it mean for one person to have more digital presence than another? What exactly is that worth? It seems like it will take a few years for these questions to get fully worked out.