Trying to keep a group of people working together on something over the internet is like herding cats. You typically end up with a few core members which will stay in communication, surrounded by an ever-changing group of people who work on, or poke at, things without ever truly understanding them. I like to call that core group 'The Batpod.'
As sneaky said, the hard part is knowing how motivated people will be. You'll find people who'll go absolutely gaga over your project, and then do absolutely nothing to help you with it. You're focus on portfolio work might change that, but not by much.
So what is the base project, and what is your role within it?