Zipcar, the car sharing operator which has major presence in the San Francisco Bay Area, has been acquired by Avis Budget Group, the car rental operator. AVIS said it has agreed to acquire Zipcar for $12.25 per share, or approximately $500M. Avis said it now has more than 760,000 members across 20 major metropolitan areas. Zipcar will operate as a subsidiary of Avis Budget Group. Zipcar was based in Cambridge, Mass., but moves to a new location in Boston with the acquisition.