The point was (and is) that policing in the UK is based on a "service and consent" model rather than the "crime control" model familiar in the United States.

BBC: Could we tolerate zero tolerance?

Because the new operations are based on a "peer to peer" business model, "issues can arise that are out of your control, " says the 25-year-old Mr. Smith, who launched SpotHero in July 2011 as a driveway-sharing service for the Chicago market, but has since shifted its focus.

WSJ: New Turf for Sharing Services: the Driveway