Peer-to-peer car sharing startup, Wheelz, is getting a $13.7 million round of financing from none other than Zipcar. While some folks in the peer-to-peer space have tried to define themselves against Zipcar by arguing they have lower fleet expenses and are more capital efficient, Zipcar now sees an opportunity in peer-to-peer. Yes, part of the reason for Zipcar’s investment is defensive, in case peer-to-peer really is the wave of the future. But I think it’s more likely that the company is excited about closed social systems like college campuses. Wheelz has rolled out at Stanford, and similar to how Facebook began, is going after networks where there is built in trust. Zipcar is aggressively rolling out its services at college campuses to hit a demo that is ignored by the traditional car rental companies like Hertz, and the Wheelz deal is another way to get to that market. All of this can also be explained by Zipcar’s increasingly close relationship with automakers like Ford, and the fact that Zipcar wants to “advertise” cars early on to young folks via car sharing, which would give Zipcar a lot of value to the automakers.