ParkingCarma.com - Reserve your parking spot

Anyone who lives in a big city knows the headache that is finding a parking spot. It used to be that just Friday and Saturday nights were impossible but now it seems that anytime of day, on any day of the week, finding parking is a dangerous challenge. Now, ParkingCarma.com will take the stress away by allowing users to reserve a space in advance. Before heading out on the road, users can tell ParkingCarma their destination and time of arrival and they will display the available spots. Users can pick the spot that they like the best whether is be by price, distance, valet or other special needs. The system works with new technology called SmartParking, which is a network that "uses wireless sensors and interfaces to gather, organize, analyze, and process parking information from off-street parking facilities." Anyone can use ParkingCarma's space locator but only paying members can actually reserve spaces. Registered members can also store their preferences and take advantage of pre-paid parking where available.

"ParkingCarma's vision is to make people's lives more productive and support sustainable development by improving the experience of finding a place to park from one of uncertainty, frustration and fuel-wasting searching to one of ease and confidence.
Fundamentally, the top 20 US cities face increasing congestion problems because of steady population growth and the lack of property to build additional parking. This makes commuting, going out for an evening, or even finding a parking spot in your own neighborhood more and more frustrating!
ParkingCarma will help improve the quality of life and increase community development and productivity."

Even cities with excellent public transportation suffer from the pain of crowded parking lots. People waste time, gas, money and get angry when there is drama in the parking lot, so any site that has a real solution like ParkingCarma will be successful.

How exactly is the space "reserved?" What does a driver do if someone else has taken the spot they reserved?