If you are a forum owner is there any good reason to incorporate your online business so you can operate with all the advantages that a corporation has?
I agree with CM. Unless your forum is part of a business or its basically your gross income, then there would be no reason to incorporate. If you run a network of forums or something like that, then you might want to look into incorporating the network.
Never incorporate elements that deviate completely from the original purpose of the forum (unless you're changing the very purpose of the forum itself). Chances are your current community simply won't care that much and/or you'll end up over-extending yourself.