Hmm ya i did know about that. And people have been penalised and banned due to those issue earlier too.
But one more thing i would like to add to it is that Google has also said that the images can be next to ads but they should be saperated by a saperating dark line or margin so that the visitors do not get confused or the visitors come to know that both f them are not at all related.
But still its a bit riskey. You never know for what google kicks your a** later
Thats why i was a bit worried about these image hosting sites as the always contain images and no or very less content.