How should I organize my online marketing team?

As the head of audience and engagement for a newly launched online community, I am looking for perspectives and insights on how I should build and organize my team to support our aggressive initiatives for 2012. Should I build the team around the main objectives of the online community, i.e. a member acquisition team and a member engagement team? Or should I build the team around specific online channels, i.e. email, display, search, etc? Or a combination? Or some other way that I have not thought of before? I've worked and managed in both types of environments, but I wanted to hear opinions from other experienced online marketers as to what's worked/not worked for them.