I completely disagree with the current TB criteria as posted by nsx.
Creating forums is an art, not a science. If only a few posters want a forum but it's a good idea for a forum that will add value and grow over time it should be given a shot. If it fails then we have lost nothing.
In particular, I despise the bureaucratic requirement of a poster having to fill out a form in order for a new forum to be considered. Screw that. IMHO it is the job of the TalkBoard to look at suggestions with an open mind, do some research and made a determination regarding what is in the best interests of the community. Posters should not have to come before the TB on bended knee with their forms filled out in triplicate like Arthur Dent before a Vogon highway-building crew.
The TalkBoard should work for the posters, the not the other way round.
So here are my criteria for creating a new forum:
Are there a few FTers who are passionate about it?
Is it a good idea?
Is it in the best long-term interests of FT and the posters?