A new peer-to-peer car-sharing serving that links people to cars via Facebook launched at Stanford University this week. Wheelz hopes to distinguish itself from similar services by using existing social networks on college and university campuses. To help amp up the trust factor, which can make or break the decision to lend a car to a stranger, transactions are facilitated through Facebook and restricted to people with a college email address; the back-end software also conducts instant department of motor vehicle checks to weed out irresponsible drivers. The service installs customized DriveBox hardware in each participating car, and an iPhone application lets drivers unlock the vehicles without a key. (CEO Jeff Miller tells CNET News that there is no need for an Android app on the Stanford campus.) Car owners set their own hourly rates, and Wheelz takes a 40% share.