riddergrant: Well, at least you're prepared for flaming.
Honestly, most people here are going to give you useful info, either because they don't know as those aren't their niches, or because those niches are intensely difficult to profit from, and they don't want to be giving away secrets that are actually making money for them.
For a start, I'm going to point you in the direction of Douglas Rushkoff. I forget which book it is, but he does mention the way that porn and gambling are indeed inter-related by selling the ideals of a taboo.
Online or off, it relies on the same end-user / customer mindset... Accessing something that they normally cannot for whatever reason.
If I knewa bit more on the subject, I'd point you in the direction of some books on the psychology of gambling addicts and porn consumers, but I can only think of LexisNexus or Jstor as being decent places to get that info.
Downside is that you require subscriptions to both of those journal databases.