The Google AdSense blog announced they have made two changes to the Competitive Ad Filter tool. Here they are:
In the past, the Competitive Ad Filter sometimes took up to several hours to block URLs you'd entered. Knowing you've wanted a faster filtering system, we're excited to let you know that URLs added to your Competitive Ad Filter are now usually blocked within 30 minutes. We hope that this will help you quickly make changes to maintain a positive user experience on your sites.
Increased filter list size
At the same time, a growing number of you have let us know that you're running out of space in your Competitive Ad Filter. Now, you can add up to 500 sites to your filter list, more than double the previous limit. As you add new sites, please continue to keep the possible revenue impact of filtering in mind. You might also find it helpful to review our tips for using your Competitive Ad Filter.
Overall, AdSense publishers are happy with these additions. A small change, a small improvement, but very welcomed.