I always think, when someone is ASKING for a niche, then their project is doomed to fail. Things run well when people care in, believe in, live and breathe the thing they are selling/supporting/running.

If you don't having something within yourself that fits that bill then don't just try to service someone else's whim - you will never truly be 'in' it.

I've set up countless forums, sites and groups - those that did well were those that I wanted to do well, that i totally understood and that i believed in. Every failure I've had has come from me not understanding what someone else (the audience) would want out of the site, as i am not the target market.

You can do a lot of work to get yourself into the mind of the target market - but it's far far better if YOU are the target.