I don’t have any direct experience with Yahoo’s ad program. I use google Adsense on a couple of sites, and for the most part they are related to the content. It’s funny to watch the ads in the ‘off topic’ area though. For the most part the ads in the regular area of the board are able to build on the history of posts in those areas. But of course the off-topic area can go wildly off in different directions. For example, in one topic a while back we started talking about doing a custom bear like the phpBB Berties. The ads started including mentions for Alaskan “Spirit Bear” cruises.

I doubt they got many hits.

Then I go view a (much older) topic that has surely been indexed, talking about the song “Simply Having a Wonderful Christmas Time”, I get the same two ads.

And finally, I go read a topic titled “Ohm’s Law for Pirates”… and get the same two ads.

Not only that, but the units at the top and bottom of the page show the same ads in most cases.