So is ubercab connecting people with "car services" that aren't licensed taxi companies? Are these the drivers you see often in NYC when arriving at the airpor

So is ubercab connecting people with "car services" that aren't licensed taxi companies? Are these the drivers you see often in NYC when arriving at the airport? My understanding is that there are risks to using such services (like if you leave something in the vehicle you're unlikely to recover it whereas a taxi co. can usually track it down). True?