I recently got in touch with a small two-FAST-person entrepreneurial shop 2’s complement with some great ideas.
They have a few projects under the belt but their first working product for Facebook is an application you can use to send SMSs back and forth – screenshot below, link here.
At first sight this seems like a proof of concept to gain better skill at facebook applications development, which has high demand in freelance work platforms like rentacoder or elance.
At the same time though, the facebook platform is a proven way of sky-rocketing to a large scale. If you have scale, you can always figure out a business model around it. So far, the SMS app has about 550 active users (which is pretty good I think because it demonstrates the viral nature of the social interaction.)