I'm not sure it would be that hard for Google to identify the crap sites - when you go to one you either click your back button or out through the adsense that

I'm not sure it would be that hard for Google to identify the crap sites - when you go to one you either click your back button or out through the adsense that usually dominates/perfectly blends with the content anyway, Google is catching that bounce rate damn near 100% of the time.