We run a twink foot fetish site, boysfeetclub.com, which has always performed pretty well and typically had pretty amazing retention... yet neither AJ nor I have a foot fetish. My former business partner Ryan did, which is how we ended up with the site, but AJ and I have managed to learn what the foot fetish people seem to like, and are able to produce content that people enjoy... so I think it's definitely easier to have a successful fetish site if you have and understand the fetish, but I also think you can pull it off without personal attraction to the fetish if you take the time to really learn it.