Because, the first reason is: you're wasting time, so that should make you think about it. Then adsense orders ads by ecpm, not by cpc. So you want to block low cpc ads (even that you won't be able) but maybe that ad has a very ctr because it appeals to readers, so its ecpm is very high, so by blocking it you're losing money. Then also what you see is not what other people see, so once again time wasting.. Now, of course if you're convinced by it, then who am I to tell you otherwise? I have no interest in your earning more or less money since I don't get a share, that's why I'm not going to try harder to convince you, I just wanted to express my opinion about it, since we can read many more posts about why doing it than posts about why NOT doing it. And by the way I totally agree with you that adsense should provide a feature for publishers to say: I don't want to display ANY ads which overall ecpm is lower than $X. If you don't have any related ads with a ecpm matching my minimum, then don't display anything and revert to alternative ads or collaspible ad units.. But I also wish paypal would pay interest on the money sitting in my paypal account.. Speaking of adsense I also would like them to put back their referral links, etc.. many things we wish