I know this has been talked about all over the place ad nauseum for a while now, but I have to admit that I love Google ads. Targeted advertising is much better than the usual scattershot methods of the past. I'd rather be inundated with requests to purchase things that I might actually be interested in, rather than garbage that I couldn't care less about.
The system works fairly well, too.
When I'm looking at a post or email regarding homebrewing, I get ads for equipment to make beer/mead/wine at home.
When browsing the subject of computers, I get ads for hardware and software.
And when I'm looking at science or atheist related posts, the vast majority of ads are along the lines of "how to pray the rosary", "evolution is a fairy tale", and "learn about Jesus today."