To be perfectly honest, your niche is something you perhaps don't want it to be : porn. There is a market, there are customers, and it is where recommendations

To be perfectly honest, your niche is something you perhaps don't want it to be : porn. There is a market, there are customers, and it is where recommendations would be highly valued. Furthermore, users are willing to rate, there is a lot of tagging going on, the tags are quite detailed, and the benefit from being able to recommend specific items for specific tastes that are not widely found, means that these 'niche' users are easy to monetize. Your service is perhaps a bit vague at the moment - when you spin off a section that does targeted porn recommendations, you're going to become instant millionares.