Owning a bike isn't really that good for commuting. I use Citibike to go to work and pretty much anywhere else they have Citibike docks. People always ask why I don't just buy a bike. I had a bike. It got stolen. If a Citibike gets stolen, that's not my problem. Moreover, I don't have to try to take it on the train, or carry it into a building, or find a place to park it outside where it won't get stolen or vandalized. I've seen people in my neighborhood with giant bolt cutters going after people's bikes. Then there's always flat tires, bent rims, brake pads, etc. maintenance cost. Why bother with that. Cars are really the same way. What's the point of owning a car? So you can drive out to Walmart somewhere and buy ten bags of stuff every two weeks? Just order it and have it delivered to your door instead.
But those shared bikes are miserable to ride. The frames are heavy and not stiff enough, no suspension, no pedal clips, etc. They're fine to go a few blocks but for anything longer it's an unpleasant experience.
It's not hard to make your bike less attractive to steal. Big fat D lock. Shitty looking seat. Locking nuts for your wheels. Parking in a rack amongst more attractive bikes. Taking your bike into your apartment. Not giving a fuck about what your coworkers think about your bike parked in the loading dock.
If you are commuting, I wouldn't pay more than $100 for your bike anyway. Unless you are biking 100 miles a ride, you'd be hard pressed to notice a huge difference between a scratched up steel frame trek you found on craiglist and tuned up vs. some carbon fiber precision instrument imported from Italy. My maintenance costs are taking it to the bike shop once a year for a tune up - $60 and they give me new pads. I haven't had a flat since I bought gatorskins, and even though I suck at changing them, an inner tube is cheap and takes less than 30 mins to change. Those dollar or two rides on bike share really add up if you start relying on it heavily.
I get that it sucks hauling in a bike on a packed subway, but in the u.s. that's only really a concern for commuters in nyc. Even L.A. is a bike utopia once you get comfortable with traffic grazing your elbow and cutting you off all the time; it requires thick skin, and planning your routes a little differently, but you will always be faster than a car in traffic due to filtering.
If you live/work in a larger building you will probably have dedicated indoor bike parking, which solves the problem of keeping your bike safe at least at those two endpoints.
