Uber now valued higher than 72% of Fortune 500 — with some big asterisks

After the latest $1.2 billion funding of Uber, the mobile ride business is valued at about $40 billion which would put it's estimated worth ahead of 72 percent of the Fortune 500.

Its backers are banking on the company becoming more valuable than such well-known brands as Harley-Davidson, Kraft Foods, Delta Airlines, Charles Schwab and KKR.

But Fortune magazine points out that if it was publicly traded today the San Francisco company led by CEO Travis Kalanick wouldn't even be close to making its annual tally of most valuable businesses.

Uber is one of the companies at the heart of an effort by the city of Dallas to define regulations for transportation-for-hire services that included Uber's competitor, Lyft, taxi companies and limo services.

That's because its revenue, according to figures that leaked out a few weeks ago, are less than half as high as United Rentals, the bottom company on the Fortune 500 which posted $4.9 billion in gross sales for 2013.

The comparable figures which Kalanick was reportedly showing when he raised funding earlier this year showed the company with $1 billion in transactions in 2013 and projected between $1.5 billion and $2 billion this year. Uber's 20 percent take at the high end of its projection for this year would be about $400 million.

The other problem with such comparisons is that it is based on what private investors hope that Uber will be worth some day. All but 21 of the companies on the Fortune 500 are publicly traded, so their valuations are based on what public investors believe.

We won't have a comparable number until Uber goes public.

To date, Uber has been able to weather a barrage of negative publicity from regulatory fights and the hubris of some alleged private misstatements because its private investors are standing by it. Public investors can be far less forgiving of bad news, business threats and scandals.

Cromwell Schubarth is the Senior Technology Reporter at the Silicon Valley Business Journal.