Heard that Yahoo bought BuzzTracker from Marketing Pilgrim.   I looked at BuzzTracker last year and looking at it today, it seems to have improved quite a bit from when I last looked.

I guess the sources of Buzz are hand picked and maybe, where they got creative, is the way the information is merged and chosen.   I find the acquisition more interesting in that Yahoo felt it needed BuzzTracker - I'm not that impressed with the BuzzTracker platform itself.