While it shows me something about the people, what I found really compelling was looking at the Popular tab which gives a pretty good indication of what the best content is on my site. Christy sited on of my old posts An Aha Moment - del.icio.us as Indicator of Valuable Content - Importantly My Content.
I still think this is a good indicator and the Diigo popular tab on my site community seemed like a pretty good list of what the most compelling content was on my blog.
This is a really neat feature and I'd guess that given a couple of widgets, Diigo is going to get some traction.