I think the solution would be variable pricing, much like buying or selling a financial asset. If the rates for things could be adjusted to encourage activity a

I think the solution would be variable pricing, much like buying or selling a financial asset. If the rates for things could be adjusted to encourage activity around some number (say, to keep the number of available cars in a region at 1 for every 10 zipcar members), using some real data, they could just let people drive cars one-way. If it turns out that everyone wants to borrow a car from A and return to B, that just means it's too cheap to do so, or it's too expensive to borrow from B and return to A. It would certainly be an interesting model to try.