Facebook stock jumps even as more insiders able to sell

About 800 million Facebook shares became tradeable today, but for once, the bulls have something to cheer about.

In other words, the stock is jumping today even though more insiders now have the opportunity to unload their holdings. Shares closed up 13 percent at $22.36, a welcome jump for investors who have seen a steep decline since the stock started trading at $38 in May.

Today's lockup expiration meant the largest set of Facebook shares available since May could hit the market. Many had expected Facebook's shares to take a hit, but instead, it appears most investors are holding onto their stock.

That partly could be because people are becoming more comfortable with Facebook's business, particularly its push into mobile, Sterne Agee analyst Arvind Bhatia said.

"When we had previous lockups expire, there had been a lot of doubt about the fundamentals, which led to more aggressive selling," he told CNET. "Going into this particular lockup, people seeing their shares unlocked are feeling better about fundamentals and the shift the company is apparently successfully making to mobile."

Doubt about Facebook's ability to generate money from mobile is one factor that has dogged the company. However, Facebook last month gave a strong third-quarter earnings report, and CEO Mark Zuckerberg said the company can make money on mobile. While still early in the push, Facebook's Sponsored Stories alone, which are the ads that appear in news feeds the way a post from a friend would, are generating more than $1 billion in revenue a year from mobile, and the figure is growing fast.

Even if some insiders wanted to sell, they could be waiting for shares to rise.

Another likely factor is that so-called short sellers aren't pouncing on Facebook as much anymore. Such investors believe a stock will drop, so they borrow shares and then sell them. Because they believe the price of the shares will fall, they assume they can repurchase shares at a lower price, keeping the difference.

As the Wall Street Journal noted yesterday, fewer bets are being made that Facebook's stock will fall more than it already has. The number of shares being borrowed -- a proxy for short selling -- has declined by almost 40 percent this month and is at the lowest level since June, the Journal said, citing research from SunGard Financial Systems' Astec Analytics unit.

Updated at 2:30 p.m. PT with Facebook's closing stock price.