I think you will find prett mucj most people use it to block out low paying ads rather than competitors.
Hmm but if they succeed in getting high paying ads.. then imho its bug in adsense algo which is being exploited in some niches.
Apparently a lot of people have mixed results. But my earnings did improve. I didn't use all that was in the list, just the URLs that I think would show up. I also use the adsense preview tool to check on ads when I get really low clicks and block those out as well.
WHOA! ad blacklist i used it yesterday, this morning, when I come back from my classes, i saw my ecpm in xxx range!
I just added the list few days back. Now my no. of clicks are reducing. today there is no clicks at all. So, wondering whether I can keep it or remove it. Will wait one more week. So that, I will get better scenario.