Can a company that didn't exist five years ago, an upstart with a knack for angering regulators with the power to close down its business, really be worth $US40 billion?
That's the figure that had investors from Wall Street to Silicon Valley abuzz after Uber announced it had received more money from venture capitalists than any private company this year.
"It gives me a nosebleed," says Sam Hamadeh, CEO of PrivCo, a research firm. "You're being asked to buy on pure speculation."
The cash infusion from investors - $US1.2 billion for a small stake - comes at a time when values for private companies backed by venture capitalists are rising fast.
New investments in Dropbox, a file-sharing service, and Airbnb, a website for people renting out their homes, have sent their valuations soaring.
But, at $40 billion, the prize may go to Uber. That's more than double what investors valued the company at just six months ago.
With an easy-to-use app, the company promises to tap a big market that links drivers and customers who need rides. But it also faces regulatory hurdles, competition and questions about how it will make money.
Uber offers car services in 250 cities in 50 countries, up from 60 cities in 21 countries just a year ago.
It has its sights on expanding into many other businesses, like delivery services.
"Based on its current car service business, you can't make the case (its valuation) is even close to $40 billion. But that's the not the pitch the company is making," says PrivCo's Hamadeh.
"They can take on UPS, FedEx, even the Postal Service."
