> I am surprised that there isn't a more niche advertising provider for the more controversial sites There are (specifically for NSFW websites, at a minimum) b

> I am surprised that there isn't a more niche advertising provider for the more controversial sites There are (specifically for NSFW websites, at a minimum) but they aren't as lucrative to the sites themselves. Fewer advertisers are willing to do business with random small ad exchanges (for a variety of reasons, fraud among them) and the ones who do don't generally spend much. Remember: most ads online are bought and sold via auctions. If demand/competition is low, the highest bid won't be much.