I'd had some good success with Facebook and my last company. We'd had enough Facebook fans that we were able to run regular contests a few times a week and to

I'd had some good success with Facebook and my last company. We'd had enough Facebook fans that we were able to run regular contests a few times a week and to use it as a platform to talk about what we were excited about. The interaction that's possible means that even if you seed it with the sort of content you'd use in a newsletter you need to have time every day or so to handle the interactions that it generates.