Over the years that we've run the google banners we have made this huuuuuuge list of stuff we don't wanna run. And there's room for more.
Recently, folks have pointed out some google banner stuff where the ads go to less than wholesome sites. I think I've banned those. If anybody spots anything else that doesn't seem like a good fit for JavaRanch, please let me know and I'll block it.
Currently, the google banners seem pretty okay. Very on-topic. A good fit for us.