In real life, freelancers rely on referrals to get good work. I know that I have a small rolodex of people I send people to -- including a preferred designer, a preferred JavaScript guy, etc.

What would be cool is if you made it invite only - but also showed the graph of invites & connections. So, for example, I know that if I invited my designer friend, I would be judged based on her work. This velvet rope could help recreate the quality threshold we all experience in the real world.

To keep it being a second-class LinkedIn, you could limit referrals -- say, you only get x every year, or you can only recommend x people per field. Imposing a cost on referrals / connections could keep people using them in the best way -- not like the people on LinkedIn with 1000 connections.