Imagine my surprise when I noticed ads on this blog! It's all going to charity and too cool to opt-out of. If you don't see the ads then it's because they're not targeted to you.
What on Earth am I talking about? I use Outbrain to provide the star/rating system for my posts. As this is a blogger.com blog and not Wordpress I don't have YARPP and use Outbrain instead. It's in these related posts that the ads have started to appear.
I think I know how this works. Advertisers use blogs to connect possible customers to other good editorial content. If a blog is saying something cool about you - then wouldn't it be great to give that blog post some oomph. Outbrain does this. It also does this openly and with the ad disclaimed (an interesting ethical point when compared to link building on behalf of positive blog coverage).