It is interesting to see the different opinions of all of you. @premium domains: Is it possible to give us some stats for let's say 2 weeks or even better a month and tell us your results. In this way we will have a scientific basis.
Should i just choose to block 200 mfa or low ctr sites like yahoo too, whats better choose both or just mfa?
I have some good succes with filtering mfa and low paying sites. CPC increased from 0.03 average to 0.19 average. I like it!
My ecpm has been 40% higher on average since I filtered MFA sites. Just my experience... time will tell.
I wish that Google would let us filter by advertiser. I got half of my filter full of whoever the weasel is who owns sites like this: http://onlyaccountingsoftware.com/ He has thousands of sites like this, and uses the same template.
25% isn't so much and also this don't mean it is because of filtering lower paid ads. CPC can vary from day to day for 100% also.
I didn't read only headline, I read first few posts, but really not the whole thread. It would be waste of time for this topic...
On a semi-related note, here's a writeup of mine showing how you can find out how often Google Adsense shows PSA's and from which URL's. If you filter MFA sites, you probably want to check to make sure you don't get more PSA's.