MadeWillis - 6:31 pm on Apr 14, 2009 (gmt 0)

Is there a reason why the search partners can't be blocked or advertisers choose the search partners they want the ads to appear on?

Yes, there is a very good reason. Money. The only thing you can do is block up to 500 domains individually.

Despite parked sites looking spammy and like just plain crap, I've seen some good sales from them in the past.