cagey1: one annoying thing that is on the rise is that there is a proliferation of sites which scrape Google groups. Have a look for all the ones scraping alt.comp.freeware for eg., -- to make it look like it's their own forum. The argument, that you can't prove intent, is one I would not agree with in a million years. Those are, in fact, blatant dead-simple examples of creating a site merely for the intended purpose of littering the Net with Adsense.
Which brings me back to my first point above: with (a)so many Adsense ads out there, and with (b)so many low-converting sites because of this -- it keeps advertsing costs low and protects the insidious bottom line. (At the expense of so many respectable webmasters/site owners, like those ones who took a s-kicking because of Bourbon...)