I used to have a job whose primary responsibility was overseeing technical support fora on compuserve, which moved briefly to a badly implemented web log, and then settled on NNTP-style newsgroups run off of a corporate server.
In general, I think having a corporate-sponsored community around [insert name of item here] can be a *great* idea --- nothing helps build loyalty, or a sense of being listened to and understood, like participation in a community; and if it's software you're into, providing a place for developers and users to talk to each other, and exchange ideas, can be critical to the success of the product.
However, some warnings:
The largest use of such a discussion site is going to be for technical support. If your company charges for technical support, your techies can't be out giving away free answers on the discussion board; their time will get drained away to nothing, and so will your revenue. A system has to be set up to encourage the users of the board to help each other; while this sounds easy, in practice it's hideously difficult.
Having members of the company participate in the discussion is touchy, too. A lot of customers, and upper managers (how big a difference is there?), will assume that company people posting in public do so as official representatives; establishing the demarcation that these people are posting as individuals who happen to work in this company takes a fair amount of work, and the work is ongoing --- you constantly have to remind people, in a friendly fashion.
In addition to profanity and spam control (we have to do both), you also need to perform leak control --- every company has secrets that shouldn't be splayed across the boards --- and misguided flame control; that is to say, people who think they know one of the company's secrets (and don't) may mislead the rest of the community into believing them.
You really shouldn't be doing this unless you're (a) really small or (b) willing to have the company devote a full time person --- not to maintaining the code, but to maintaining the atmosphere of the community, stamping out flames and spam, and the like.
Just some things to think about --- if you want to talk, drop me a line: aphrael@misanthrope.NOSPAM.discontent.NOSPAM.com