Do you take advantage of the ability to block ads that are low paying (either by guessing or using some kind of tracker) on Adsense and/or YPN?

I don't use a tracker but I do ban sites like Ebay and other sites that just reek spam. I find all the Ebay ads to be very annoying.

I block ebay, truelocal and starware (or starwave, cant remember the actual name).

Personally, I think adsense needs to have some sort of quality control in place to prevent all this spammy advertising. Nothing more irritating than seeing "fantasy football ringtone" in one of the ads on my forum. What, exactly, would a "fantasy football ringtone" sound like?

Well if it was about my fantasy football team probably a crashing sound effect

I've never taken time. Have you guys seen an increase in PPC because of this practice?

Yep you should block all of the MFA sites too. Here is a good read:

Blogger Skills » I Increased My eCPM by over 25% by Filtering MFA Sites

Nice I actually had an ad on my politics site that went to a landing page for an affiliate offer.

Blacklisted that one.

Interesting read, thank you Rex. I guess what I don't understand is how filtering them helps. I thought Google showed ads with the highest bids first? Wouldn't filtering them out bring in ads with lower bids?

Hmm *thinking as I type* I guess if they're well written ads they could steal clicks away from the higher bids. So by filtering those ads, you get clicks on the high PPC ads. Is that the idea?

Here is a good discussion on blacklisting ads with points for and against Google serving the highest paying ads all the time.

Black listing low paying ads - vBulletin SEO Forums

Mix Cool Whip, cream cheese and powdered sugar in a bowl. Mix pudding and 3 cups milk in another bowl. Pour into Cool Whip mixture and fold together well. Pour over cookies. Crush rest of cookies and put on top. Refrigerate and enjoy.