I don't think you're at all correct that they are less traceable than yellow cab drivers. The government bureaucracy makes it much more difficult to fake credentials and make yourself untraceable.

With UberCab, it looks like anyone could steal an iPhone/credit card, download the app, and sign up as a driver all in the space of an hour.

I think you wrote "less" when you mean "more". Assuming that's what you meant, I disagree. From their website, it looks as if UberCab requires drivers to be a livery company, so gov credentials are required either way.

The only way I can see the stolen iphone game working is if you steal the iphone from an UberCab driver, or convince UberCab that you are an independent livery and then rape someone before the stolen iphone gets cut off.

In contrast, a legitimate yellow cabbie just needs to put his coat on top of the taxi license and make sure the victim doesn't see his license plate # as he drives away. That same game won't work with a legitimate UberCabbie, since there is an electronic record that driver X picked up passenger Y.

True. I think it's common for the owner of a medallion to let someone else drive the car illegally.

Well, with ubercab you have a record of who the driver and passenger are before you even step into a cab. I can't tell you the last time I bothered to look at a cab number or license.