Just as @mattclarke has already stated, I don't see it rewarded. In part I think its due to the public nature of the blockchain, but also I think its because original content is still valued highly amongst steemit users, and a lot of these porn posters are just reposting crap from the internet.
When they discover that they aren't making money from it like they thought they would, they will eventually give up and leave (i hope).