[edit] Also its worth noting that the reason people would risk unlicensed cabs in London was that taxi licenses were so strictly controlled that prices were quite ridiculous for many.[edit2] And that the solution to the issue in London was to license the minicabs where trying to shut them down demonstrably failed.
"Taxi Satelital" is a taxi company valued for its safety and overall ease of use, that subcontracts each ride to a pool of licensed drivers (like uber).
A young woman accused one of its drivers of drugging and abusing her. Everyone assumed she was right and went all "duke-lacrosse" on the firm, which we assumed will have to go bust soon. The next day, the CEO appeared on TV with a CC video, the phone call audio, GPS records, and even one witness, showing that she was indeed making it up.
After seeing this happen one too many times, I think its prudent if we withhold judgement and let the police do their job. That said, I do believe unlicensed drivers are a huge issue in thefts, kidnappings, and rapes in many parts of the world (London as you quoted, but this is also common knowledge in most of Latin America)
Background checking, while far from foolproof it's both a deterrent and a preventative measure.
Higher barriers to entry, if it takes significant amounts of effort and money to be able to drive a cab then people are both less likely to risk it and going to try something else to have their 'fun'.
(I also do not believe that the ride sharing services are particularly risky.)
"Laws don’t exist merely to frustrate the business ambitions of coastal hipsters: They also exist to protect the more vulnerable members of society. Back home in London (where such statistics are available), 11 women a month are attacked in unlicensed cabs, and unlicensed drivers are responsible for a horrifying 80 percent of all stranger rapes. If Uber doesn't have to follow licensing laws, then neither does any Tom, Dick, or Harry who chooses to paint the word 'TAXI' on the side of his car, and start offering rides via the Internet. A disruptive CEO will shrug (and there's a foreshadowing word) and insist that it’s not his fault that such criminals exist."[1]
It appears this critic was right.
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[1] http://pandodaily.com/2012/10/24/travis-shrugged/
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Edit: added "It appears," which more accurately conveys my position.