It's just one more pointless feature to ignore, like a row of "submit this page to some other random website" buttons, a column of video comments from some random video startup (Seesmic?), ads for Wordpress themes, and other typical Web 2.0 detritus.
I'd like to think the problem stems from the fact that a lot of Web 2.0 startup startupers are extremely young and think that a Digg button, a bunch of startup plugins, and a column of AJAX goodies will add to a page's design rather than compromise it. Unfortunately, these things are so widespread that I fear some people have bought into these things as actual effective tools, which saddens me somewhat.
