[Bishop]

If the site is marketed specifically to one niche then the site should be all about that niche. However if the site owner has the means to provide other areas within the site that provide additional content then it should be provided. Even if your heavy into a fetish that doesn't mean that is the only thing that will get you off. You might be in a mood one day and want something that is the opposite of your normal taste.

Having additional content is not going to hurt the site. If anything you may meet the consumers needs for a little while longer before they cancel and move on to the next site.

With that said I'm not talking about a mega site that is the same backend for a bunch of different front doors. The site should really be built to the niche it is represented as. A link in the primary navigation that leads to a warehouse of other content is fine as long as it doesn't take away from the flavor of the site.