Earlier this year, GM unveiled a peer-to-peer car-sharing service, expanding its Maven platform to allow GM owners and qualified lessees to rent out their own vehicles. At the time, the company said the service was in beta in Chicago, Detroit and Ann Arbor, Michigan, but GM has now announced that it's bringing the peer-to-peer car-sharing service to 10 US cities in the coming months. By the end of the year, the service will be fully launched in Ann Arbor, Baltimore, Boston, Chicago, Denver, Detroit, Jersey City, Los Angeles, San Francisco and Washington, DC.