And no they're not going away, and yes there's a limit to what cities should do to discourage them. But making it easier for carsharing companies is really about the best thing cities can do to help reduce the number of cars residents have. It's all carrot, no stick, and makes it possible for people who need a car occasionally to go car free.
I'm not sure how long I would have made it without a car if not for car sharing. Cars are useful things and occasionally you need one. I'm not a fan of borrowing friends' cars, and fewer and fewer of my friends actually have them anyway.