uberThe global taxi demonstration that snarled traffic in London, Barcelona, Paris, Milan and Madrid yesterdayto protest car-sharing leader Uber showered priceless PR upon the San Francisco start-up, which sports a potential $17B market valuation. 

Drivers contend that Uber is lightly regulated and is n enjoying a free ride, which puts their financial livelihoods in jeopardy. 

The protest noise -- so far - -is sweet music to Uber’s ears as it reported an 850 percent increase in UK sign-ups, according to today’s New York Times. In a deft move to cash-in on the traffic mess, Uber is offering a discount to consumers.

Uber indeed faces thorny issues concerning safety, regulation and price-gouging allegations that must be dealt with if it expects to live-up to that heady market valuation.

Its success will undoubtedly trigger a flood of competitors into the ride-sharing category, which will force it to trim fares.

For now, however, Uber is riding high, thanks to the embattled taxi drivers who are trying to fend off the march of technological progress.