PRT will happen - when it becomes fiscally viable for people and companies to invest their private dollars into the entire ifrastructure of such a system - from producing the actual vehicles, to the rails, stations, hardware and software to make it work - so long as there is a profit. Large corporations can pool resources and capital to build the actual system, with the expectation of a use based fee as their payment for the amount you use it. These same companies and others can mass produce (for low cost to the consumer) or even custom make the vehicles, again for a profit. Owners of the vehicles could at their discretion rent out the vehicles when they themselves are not using them - either for a profit (e.g.: people with large sums of money to invest - say a highly paid doctor or engineer or real estate investor, or a blue collar guy who can make the numbers work and get a loan - can buy small or large fleets of vehicles to be out for rent as a business) or the average user can simply allow theirs to be rented to help defray the costs or ownership. The vandalism issue could be minimized by charging enough to cover insurance, graduating rental fees based on some type of preferred status, renting only to known persons or "clubs", and heavily protected cameras that record users as a deterrent and for prosecution after the fact(my cars would require renters to accept surveillance - perhaps others would not reguire it, but they could of course charge more for the privacy; free enterprise would regulate such a system).
In the end, once the technology becomes cheap enough for a return on investment, this kind of a system will be born.