In case you have not heard:

http://www.corante.com/goyami/archives/affiliate_policy_change_at_google_adwords.php

Basically, Google will not longer be allowing multiple ads on a given page that point to the same web page. This usually occurs whith affiliate marketers.

The bottom line is that if you are an affiliate marketer and you currently use Google to place ads to try to drum up your affiliate income, you should create landing pages for your ads rather just linking to the site where you are trying to earn credits. (This is discussed in the article listed above.)