adcelannotate = {"mobilepaywallcategory" : "MOBILE_PREM-BUSINESS","nativepaywallcategory" : "NATIVE_PREM-BUSINESS"};Uber, a service that allows riders to choose a car type and pay by credit card from a mobile phone, has in four years gone from nearly non-existent to more than 26,000 drivers, joining the city's 13,437 taxis.