The simple question what is the most annoying ad format for you as a surfer?
For example popunder (and its varieties like tabunder).
It's no secret that this one is the most profitable format for publishers, and users are already used to it, as a their fee for
free content. Got popunder on your websites?
Or other example - fake download buttons on banners. Even adsense sins with such creatures on sites with files, such as download.cnet dot com
Do you use any ad blocker? How effective is yours?