I have some sites with info relating to old electronic components, that have been doing nothing with Adsense.
Due to a hosting problem, I've had to check all my domains - and when I went to those sites, the ads were all for things like stair lifts and solicitors! I suppose it says something about the age group of my visitors ...
Back to Adsense and uncheck the "Display Interest Based Ads" box, and immediately those sites are back to selling ads appropriate to the content.
Anybody actually improving with that "interest based" stuff? ___
I did the interest based stuff for a while when it was first available to me to test. They bugged me to try it. I didn't really want to when I first heard about it. After my ECPM slowly went down for a couple months, I remembered it and turned it off. My ECPM has risen again.
Maybe it's a coincidence and it's not conclusive but perhaps ads for my site in a more lucrative field pay higher than ones that cater to the interests of the browser. Makes sense and I think it will depend on your market or niche as well. If you have crappy paying ads normally, than perhaps interest based ads would give you a bump upward.