It would be interesting to know if most publishers update the 'Filetered Ad List' in Adsense. Also do you keep updating it. If yes, how do you find out about low paying ads displayed on your site .
I had a filter list for months until Google sent me an optimisation suggestion by email. I deleted all the URLs on their suggestion
I too got one and following their advice I deleted the filter. The EPC went down drastically. I have added them again.
Its basic purpose is to remove ads of your 'competitors' appearing on your sites. Though now its more used to filter MFA sites. But recently adsense sent me message advising that some high paying sites are blocked in your account while i have blocked only MFA sites. It means its not necessary that all MFA are low paying but they are not good for your viewer's experience.
Somebody please advise me how to filter ads if i have a blogger account. Since, I cant upload files to my site folder, I havent been able to use blackadlist or adlogger
Visit the URLs manually (do NOT click them, copy and paste the URL or use googles preview tool) and determine whether or not they are MFA (spammy looking pages with lots of ads) If you think it is MFA, add it to your filter.