martinibuster - 6:05 pm on Jan 27, 2010 (gmt 0)

I think CTR is part of the factor. Remember, those advertisers being shutdown are the ones running the ads webmasters hate seeing on their sites. But apparently Google was running them because the Internet public liked clicking on them. Even if they're only paying pennies, they make up for it with more clicks.

This was noted in a big thread here a few months ago when the shakeup began.