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Facebook founder Mark Zuckerberg hasn't moved the company quickly enough toward an IPO for some shareholders. According to reports, some have begun trying to sell their shares at a steep discount to the $15 billion valuation afforded by Microsoft's $240 million purchase of a 1.6 percent stake last fall. One such shareholder, supposedly a Facebook employee, tried to sell 0.25 percent of the company at a $5 billion valuation in April and could not. More recently, a shareholder represented by California money manager Bill Dagley — possibly the same one — has been trying to move shares at a price that values the company around $3 billion to $4 billion. Back to your caves, Facebook bears. That shares are on the block at a price much lower than Microsoft paid does not suggest Facebook's value is spiraling downward.

There are two valuations for startups like Facebook — the one set by the company's most recent investment round and an internal one, often lower, established for tax purposes. Why the discrepancy? For one thing, Microsoft bought preferred shares, with some liquidation rights, while employees get common shares, which could get diluted. Going by the reports, it sounds like common shares are the ones up for sale. There's also no established market for Facebook stock; shares that are hard to unload get discounted accordingly.

The selling spree does reinforce what we already know: Shareholders — including employees, some of whom even took to cheating the company out of a $600 housing subsidy — want Zuckerberg to hurry up and sell or take the company public.

Too bad for them. Zuck controls three-fifths of Facebook's board and is in no hurry.

The silver lining: The difficulty in placing their shares with a buyer may pay off in the long run. Instead of selling their Facebook shares at a discount, these shareholders will probably have to hold on to them and — despite themselves — make a whole lot of money when Zuckerberg finally does take the world's most popular social network public. Just so long as Facebook's sales team keeps treating ad buyers to juicy steaks.