I've noticed on a couple of my sites that the AdSense is not showing ads but showing those public service announcement things.
It's not all of the sites, just a few. Namely the top performners.
So, I was poking around for info on the AdSense site and group. Apparently you get those ads when the "Google algorithm" deducts that you have "adult" or "mature" content on the site.
The problem? I don't have that on the sites!
I find it suspect that the top earners are the only ones affected.