Facebook's Stock Options

Brin "We really started to grow (Google) during the bust of the dot com bubble," he said. "Their timing may be somewhat inverted." Google, he said, benefited from the discipline imposed on it by the bust. "I think that's an extra challenge that they face," he added"

it's obvious he is considering Facebook overvalued

Can anyone confirm that the stock options offered from now on must be based on the valuation of the company from the most recent round of funding? I have a hunch Facebook's internal valuation's a ton short of $15 billion.