I've worked on some adult stuff in the past. I have no issues with it but I won't be doing anything in it again. Mostly because it's such a relatively small and boring subset of the world.
I will say that it involved clever abuse of search engines to generate traffic for obscure fetishes (all of them). It might not work today.
Then again, now that I think of it, see http://xkcd.com/305/ for a pretty good summary of half of pg's Plan for Pr0n (the other half shall be left as an exercise for the reader).
It wasn't a backup plan though, just an idea for a practical joke like Trevor's Information Supercollider.