Do you want your site to have a community feel to it or would you rather stick with something simple (like live chat for example). Some sites work great with a forum, but keep in mind you will need someone to run the forum too (keep the spammers and trolls out, keep the enthusiasm up and help to be a part of the community). Forums can fail if no one is there to help out, having a god presence on your forums helps to let your community know that you really do take a part and not just as the boss either, it shows them a way that you can connect with them on a personal level.