Beware of anything that adds more corporate zip and removes some of the people’s flex. Despite the companies’ predictable spin – more cars for everyone! – it is hard for dedicated car-sharers to believe that Seattle-based Flexcar getting sucked into Boston-bred Zipcar bodes well. To outsiders, it makes sense. Both car-sharing companies are built on one of the best ideas since the cup holder: What if you had easy access to a nice, clean car only when you needed it and otherwise it was someone else’s responsibility? Both started out charging members modest fees to reserve nearby vehicles for short-term use, potentially saving thousands a year. (Disclosure: I know it works. I’ve got Flexcar accounts in Portland and Seattle, as well as other cities.) The most innovative part is that members pay one fee for gas, et al; no need for their own car insurance – which as you know, if you’ve tried, is downright tricky to get when you don’t, um, have a car. (There has been some fighting in Seattle over rental-car taxes on Flexcars; other host cities are not so lame.) So, why not merge the two and have more cars, more buying power, greater visibility? Well, in short because “sharing” doesn’t stand up so well against the corporate-profit model. The warning signs of this era were already here. Since 2005, Flexcar’s been in the hands of Steve Case, former head of AOL. In the past year his share of the company has grown, and prices have gradually gone up, user rules have multiplied, and Flexcar has slowly become StiffCar. Fewer free t-shirts, even. Maybe Zipcar will surprise us and use its bigger clout to expand car-sharing throughout the country, saving money and emissions as it goes, actually reducing rates so more people can use the fleet rather than maximizing its urban profit centers by jacking up rates and rules even further. Wouldn’t that be great?