It's one of many casually accepted, unchecked assumptions in Silicon Valley: Peter Thiel, the cofounder of PayPal and Facebook investor, is a billionaire, right? Leaked documents from his hedge fund, Clarium Capital, show he's not.

Thiel, according to a 2006 Bloomberg profile, has invested his entire liquid net worth in Clarium. That's not quite technically true: Thiel has actually invested his money in a separate account managed by Clarium according to the same strategy his firm uses for outside investors. (Clarium has two other such separately managed accounts, but they are small in value.)

These matters are disclosed to the investors Clarium courts. One forwarded a copy of Clarium's marketing materials to Valleywag. Figuring out Thiel's holdings is a simple matter of subtraction.

Clarium LP, the name of Clarium's main fund, had $1.7 billion in assets under management as of March. The firm's "strategy assets" — total assets, including separately managed accounts — add up to $2.1 billion. So the ceiling on Thiel's liquid net worth is $400 million. (That's not counting his 5 percent stake in Facebook, recently valued at around $100 million.) After losing roughly $5 billion in assets from bad trading and client withdrawals in the second half of 2008, Clarium has continued to perform poorly, entirely missing the recent market rally.

So who cares if he's a hundred-millionaire instead of a billionaire? Thiel does, for one. He did not make nearly as much from the $1.5 billion sale of PayPal as he believes he deserves, according to people familiar with his thinking — the source of a long-simmering feud with top Valley venture-capital firm Sequoia Capital, one of PayPal's backers.

And a perception of outsized wealth is the source of his newfound social standing in Manhattan, where he recently relocated. It's the reason why he gets impromptu dinner invitations from the likes of New York Mayor Mike Bloomberg. It's the reason why people pay the slightest attention to his crackpot social theories. Take away that crucial tenth digit on his net worth, and he's just another indistinguishable member of the averagely ultrarich.