I found this piece lacking a key item - the fact that many zipcars are Toyota Prius models (at least in the Boston area). Given that the primary demographic for their customers are urban, short-haul drivers and the Prius is most efficient in city driving, I would think that strategically this is a pretty big factor. Gas costs are minimized, plus the company is getting the most out of its up-front higher investment in a Prius vs. a Chevy PT - not to mention being that much more of a green-friendly alternative for those who find that attractive.