I currently host Google ads on this blog, and I've really mixed feelings about it. I have Google ads deployed across most of my websites without any particular issue. On my Popular Science book review site, for example, when I just took a look, the home page ads were for things like BBC Focus magazine and New Scientist. Which seems entirely reasonable and not in any way a problem.
But the trouble is, Google's magic algorithm for determining what to display insists on displaying self-publishing adverts here. Now some of these are, without doubt, respectable - but there is a certain type of "we'll publish your book" advertiser that is, how can I put it, lacking in morals. On the other hand, I certainly can't say the specific ads that come up on a particular day are bad. And sometimes they can be quite amusing. A few days ago, one ad was for a literary agent, the second said "you don't need a literary agent."
For the moment I'll leave them there... but they're under consideration.