[withdavidli]

>Surely it can't be cost effective for people to be repeatedly parking, selling the spot, then driving until they find a new one, but that's the only real abuse I could see of the system.

This is would be the abuse and main concern. The parking situation is bad enough as is without cash incentive to keep a spot longer to see if they can get money from it.

People have brought up in other posts about how it's not worth a person's time to squat/hoard parking spaces. This is very subjective, but the comments are understandable since there are a lot of developers on this board. Last time I saw, a person can sell the space for up to $20. That's a good chunk of money for most people if they can do it once an hour. If people choose not to disclose this extra income they won't be taxed on it (disclosure: I'm not sure if a reporting feature is built into the app).

$20/hr tax free is equivalent to ~$35/hr pre-tax. That's a fair amount of money for most people. I do realize that at $20 a person can just park in a parking garage so it most likely wouldn't be that high unless the driver is spending the entire day in SF.