Edit this post as much as you want, but it needs to be brought forward to show that reputable SEO's do care about quality and frequently question the tactics of those that do things that reflect poorly on our integrity and occupation.
Lately I have noticed what cannot be classified as anything but "personal search engines" using AdSense. I'm sure you have also run across the "high ranking" sites with domain names like something2something.com. The sites have nothing but search scripts on them and ads.
How can it be that Google ranks these sites so high?
How can it be that Google approves of and allows AdSense use on these sites?
Personally, I'm getting kinda tired of seeing these poor quality, no content sites get rich off AdSense while providing nothing more than a poor quality search mechanism which appears to me to be in direct violation to the AdSense rules.
It is likely through the major loophole in AdSense. You can submit one site (your cleanest, most TOS-following site) and then you can put that AdSense code on any of your sites. Of course, you are supposed to make sure that they comply with all of the terms/policies/faq, but it is quite obvious that people are not doing this. There are many, many sites out there that have no business running AdSense.
From the FAQ
4. Can I show ads on more than one site?
Yes, and you don't even have to let us know because we'll automatically detect new sites that contain the AdSense ad code. The HTML code we provide you with is valid for any page in any site on which you want to display AdWords ads. However, you may only display AdWords ads on sites that you own or on sites that you are legally authorized to act on behalf of for the purposes of Google AdSense. We also monitor all sites in AdSense to ensure that all pages displaying AdWords ads comply with our program policies.
I supose jbgilbert is talking about a lot of sites without real content but a script which makes pages for one or two keywords.
In example, if you search "chalet granada" the four first search results goes to pages without real content but a static search (maybe in Google) made by a script; you have the same results for "chalet cadiz", etc. These sites have thousands and thousands of pages with thousands and thousands of keywords but, again, no real content. The sex keywords search results are plenty of sites like this: script -> keyword -> redirection.