Well, if you seriously want to believe that Google is just sitting back and ignoring search spam, you're welcome to do so. But if you want to believe that, you'll have to ignore a lot of the Webmaster complaints in this forum. :-)
As for AdSense, one of the most common thread topics in the Google AdSense forum is "My account has been disabled." Another is "Smart pricing has discounted my click earnings to almost nothing." Between slashing and starvation, Google seems to be making at least some effort to keep the more questionable AdSense publishers in check.