AdSenseAdvisor notified publishers via a WebmasterWorld thread that the competitive ad filter now supports up to 500 possible filters. I believe this limit is up from 200 filtered URLs from 2006.

Some publishers were able to block more than 200. In fact, I was able to block up to 500 since February 2009. However, now all publishers should be able to block up to 500.

AdSenseAdvisor said:

Most publishers are really happy about this increase.

Forum discussion at WebmasterWorld.