Sounds like this is a bike rental program, not really a sharing program. My town (naively) tried a free bike sharing program years ago. They bought about a hundred bright yellow bicycles and set up racks around town. The idea was you go to a rack, take a bike, ride it to the rack nearest your destination, and leave it there. Of course within weeks all the bikes were either vandalized beyond repair or stolen.
The same system NYC just deployed has been in use in Montreal and London for years. You have to use a credit card or similar to get a bike, so there's some disincentive to mess about (they will charge your card if you steal the bike). That said, in the first few months after London got theirs, several of the kiosks were vandalized or stolen. That problem seems to have subsided (maybe the fools figured out there was no real money in it). But cycle theft in NYC is more rampant than in London, so we'll see how it goes. My fingers are crossed, because I've used the sibling systems and they're great.
I think it's kind of designed as a bike share program with a minor bike-rental option to juice revenues from tourists. The annual membership is $95 (compare to a daily $10 / weekly $25) so if you use it with any semblance of a semi-regular basis you'll buy the yearly option, and if you're a tourist you pay the more expensive rate. It's a form of price discrimination.
It is totally supposed to be about the ride-from-rack-to-rack setup. That's why there's a 30-45 minute max before they have overages (the longer time is for the annual members).
