Only in a over-regulated, statist society would this “problem” ever arise.
Notice, as I pointed out a few days ago, that the taxi drivers and their unions are not stating the truth: that they are against these Internet-enabled ride-sharing services because they are a direct competition to their rip-off, monopoly services. Instead, as is always the case, they present their argument as protecting the public good. Their particular claim is that taxi services need to be regulated to keep the public safe.
This, of course, is nonsense. People have been using ride-sharing services for years and years. I used to use one to save money traveling from Berkeley to Santa Barbara, for instance, while attending the university. Back then, I answered an ad by someone looking to share the expense of a driver to Santa Barbara.
Let’s see how how the uber-liberal, union-infested San Francisco city officials handle this (as if there be any doubt!). In this matter, the only danger to society comes from the unions and the city in their unified attempt to suppress the actions of free citizens.