treeline - 1:04 am on Mar 25, 2006 (gmt 0)

It's not clear how much they use toolbar data yet. Once they clearly do, webmasters will setup scripts to deceive it. Works for Alexa.

They do have people employed to check samples of their index for spam. A copy of the instruction book for doing this has been published on the web, look around for it. They are primarily looking for bad sites, either not really about what they claim to be or using disapproved techniques, as opposed to dicriminating between the better of two bona fide widget sites.