Can't speak for Mobike, since I don't use it, but oBike has a very efficient penalty system. Breaking or stealing a bike results in an effective ban from the app (the cost goes up to $5/minute, then $15/minute) and users are rewarded for reporting badly parked, broken or personally-locked bikes. In several months I've only seen two instances of people using personal locks.

The bike is pretty solid and alright for commuting, but what would be the point? You get the first 5 minutes free, the first 2 rides of the day free for 15 minutes each, the entire weekend free, and you couldn't commute with your stolen bike since locking it anywhere visible would get it reported and removed almost immediately. Might as well put your card into the system and occasionally pay a dollar or two.

I think it's just because these bikes are very cheap, maybe the guard system is the major cost. Indeed, some of my friend's bikes were stolen even carefully locked(about 1500-3000 RMB). On the contrary, mobike use steel frame not Aluminium(so it's heavy), doesn't have a derailleur, and other parts are all very cheap. Which make it's cost to be very low(I can buy such a bike with 300 rmb). So just buy one will be more convenient. p.s I live in Wuhan.

AFAIK, a VC guy told me a MoBike costs 3000 RMB to produce. The costs may have come down but this was a lot!

The MoBike official cost is about 3000 RMB(used to be 6000 at first). But there is some additional cost: the parts are not standard, and the design is totally new. When they produce more the cost will come down. I don't think such a bike worth 3000, but maybe true, they can be much cheaper to achieve better experience though. Shared bikes should bear any weather or rude users, this also increased the cost. And generally, your own bike is not supposed to be in rain storm very often..