Sheryl Sandberg, COO as well as a director of Facebook (Nasdaq: FB), joined the parade of insiders who have cashed in on the company's public status. Last week, she sold shares valued at $7.44 millon after selling 353,000 shares.

She wasn't alone: Facebook General Counsel Ted Ullyot made $3.13 million selling 149,000 shares of the Menlo Park, Calif., company. And Chief Accounting Officer David Spillane took in $5.4 million when he sold 256,000 shares.

When the COO and the chief accounting officer sell, what kind of a signal does that send, especially after founding CEO Mark Zuckerberg, who collected more than $3.1 billion outright in the May 17 initial public offering, promised in September to sell no more shares for a year?

To be sure, officers of public companies are afforded certain windows to buy and sell company shares during the year, usually after an earnings report.

Facebook reported a third-quarter loss, the second consecutive loss as a public company -- $59 million, or 10 cents per share, compared with prior-year net income of $227 million, or 10 cents per share -- with most analysts projecting a fourth-quarter loss as well.

Shares of Facebook rose 12 cents to $21.30 in Monday trading, which means the price remains 44 percent below their IPO price of $38.

The insider Facebook filings were all reported to the U.S. Securities and Exchange Commission.

The trouble is all of Facebook's 4,331 employees have stock options, which come with so-called “lockups,” which expire in various months. They're handed the options as an incentive for working hard at the company.

This week alone, employees with options for 230 million shares see their lockups expire. In two weeks, another 800 million shares, including some held by Zuckerberg, 28, can be sold.

Hundreds of shareholders have already sued Facebook for misleading them in the IPO in class-action lawsuits that remain to be consolidated and assigned to a single U.S. District Court judge sometime next year. They claim the company misled them about its prospects and cite the sales by insiders in the IPO as proof they had advance warning.

After the IPO, several insiders no longer involved with management, notably co-founder Dustin Moskovitz and enterpreneur Peter Thiel, sold their entire stakes as Facebook shares swooned.

So the problem is that if there are an increasing number of Facebook shares outstanding, compared with this week's 2.17 billion, either the company has to start reporting decent earnings to whet investor appetites and attract institutional ownership or else watch its share price fall.

Or Facebook could use some of its $10.5 billion in cash and investments to buy back shares.

Currently, big institutions own only about 48 percent of the shares, unusually low for a technology company with good prospects. But the number is skewed because they include early investors such as Goldman Sachs & Co. (NYSE: GS), Morgan Stanley (NYSE: MS) and UBS (NYSE: UBS), which also earned huge fees from co-managing the IPO.

For a company to attract a value investor like Warren E. Buffett's Berkshire Hathaway Inc. (NYSE: BRK/A), directors and insiders will likely have to pledge to not sell shares for years. And Buffett will have to “understand” what Facebook does.

Last year, Berkshire became the biggest shareholder of International Business Machines Corp. (NYSE: IBM), because he claimed he understood its mission, liked the management and expected solid performance.

Berkshire now owns 5.83 percent of Armonk, N.Y.-based IBM, or 6,645,96 shares, trading at $193.65 on Monday, have gained 4 percent over the past year. Unlike Facebook, they also come with a quarterly dividend of 85 cents per share. That's $170 million pocketed by Berkshire so far this year alone!