> Now it's basically useless.
There's also this thing that even if you don't have kids (I personally don't) you don't want to sit on a car chair which has had other people's bodily fluids on it. Public transport like buses or trams is for the moment safe-ish when it comes to that, at least where I live, because not a lot of people masturbate in public or have sex on the chairs of a bus because people will call them out, but I don't see what would stop 2 people having sex in a car which they don't own (they only share it) and where nobody can see them.
There's also the non-politically correct question of what we should do with homeless people riding these vehicles? This is a real problem when it comes to public transport in my city, as the trams and buses are used as a de-facto day shelter against cold when winter comes. You really do not want to sit close to many of these homeless people in those cases, as the smell is very hard on the senses (I mean, real hard), often times you can tell a homeless people has been riding that tram half an hour ago only by the smell alone (even though he's not still on the tram). If said homeless people were to use this car-sharing thingie I can guarantee you that nobody else will use said cars after them.
There's also the thing of how do you protect these vehicles against destruction and negligence by its users, a problem encountered by many who have shared their car in the existing car-sharing projects.