I used to advertise online a great deal. Mostly, I have used Google, and to a lesser degree, Yahoo's PPC service.
Now, barely. I suspect click fraud. Hard to explain to novices, but essentially, when my ads would show up on other people's websites, I received more click (by far) than had those same ads shown up on Google. Since I felt Google was not addressing my concerns, I dropped most of my ads.
Looks like Microsoft caught someone doing it to them.
I have Google's ads up here. Those are pay-per-click. All the other ads you see on my sites and blogs only make me cash when you can buy something (If you buy from Amazon, click through my ad first, and I'll make 6%) Click --> Amazon
So I am glad as an advertiser and as an online publisher. I want to advertise more. I used to spend a couple thousand dollars a year. Now, just a few hundred. I need to trust the industry. I do not.
Good catch Microsoft.