I believe the loophole they operate under is that the ability to pick people up randomly on the street in SF requires a license, but picking people up who call

I believe the loophole they operate under is that the ability to pick people up randomly on the street in SF requires a license, but picking people up who call ahead is simply a car service and not subject to taxi licensure. The fact that UberCab has made doing the latter effectively as easy and convenient as doing the former is indeed a challenge to the old guard, whom you can bet is working behind the scenes to close the aformentioned loophole as quickly as possible. Taxi service in SF is truly horrible and is ripe for disruption. I hope these guys win. Go UberCab!