Uber is one of those Silicon Valley "share economy" startups that has amassed a multi-billion valuation on what seems like a simple idea—allowing consumers to summon a for-hire car through a smartphone app. 

The company says it now operates in 39 U.S. cities—including all big west coast cities except Portland—and 34 countries.

Uber's attempt to break into Portland fizzled last year because city regulators and the company could not agree on how the company would fit into Portland's always fractious for-hire transportation industry.

The two players in that industry—medallion cabs, which are strictly regulated and town cars, which operate with more leeway—both stand to lose business to Uber. A petition drive in Portland failed to shift opposition to the company.

Now, The Seattle Times reported today, taxi companies in Seattle, where Uber does operate, are suing Uber, alleging the start-up benefits from an unlevel playing field.

"The lawsuit, filed by the Western Washington Taxicab Operators Association in King County Superior Court, says Uber is involved in “unlawful and deceptive business practices” because, unlike the taxi drivers, Uber’s drivers don’t comply with legal requirements set by Seattle, King County and Washington state for the personal transportation industry, according to court documents."