UBER is said to be worth US$62.5 billion. Airbnb is valued at US$31 billion, Elon Musk's SpaceX Technologies, at US$21 billion, and Pinterest, US$12.3 billion.
Those eye-popping valuations regularly fill articles and water-cooler conversations in Silicon Valley, all under the umbrella of "unicorn" companies - a term for private companies said to be worth more than US$1 billion. The moniker now applies to at least 135 businesses, so they are not as rare as the name may imply.
Early investors and employees spend hours calculating how much their stake is worth. Here is some bad news: Those valuations may be a myth - or wishful thinking.
In Palo Alto, California, just down the road from many of the...