[throwaway32]

to paraphrase a certain Google executive "if you don't want somebody to know where you parked, maybe you shouldn't be parking your car"

[jnorthrop]

It's more than than just a single snapshot in time though. They are keeping a record of every car's coming and going every day. It wouldn't be difficult to poll a service like that to gather the information yourself for weeks or months worth of data.

Certainly you could drive around a parking lot everyday and get that information but that isn't very likely. It's that aspect of the service that is most troubling.