Play nice everybody
As community sites become the me too of 2007, with businesses all feeling that they need a slice of that user generated content goodness, there are going to be some rocky times ahead. It's worth remembering that even in the best run communities a reasonable proportion of the users will misbehave (at least according to the rest of the group). When your site is brand-dedicated-me-too with a veneer of user focus on top rather than truly user centric it's likely that the problems will get worse more quickly as your initial well meaning user base is forced out by hijackers simply looking for a place to hang out.
Moderation will be key (third party services like eModeration can help, for example), but it's worth remembering to plan for the worst kinds of behavior from your users from the start.