Facebook may have an impressive number of subscribers – close to a billion – but the stock reached about half of its IPO price during recent trading and more troubles are brewing.

Shares of the social media company fell below $20 for the first time on Thursday – 47 percent lower than the stock’s IPO price of $38 in May, according to news reports.

Some of the latest causes of the falling stock price are the recent earnings report (which showed costs increasing more than projected) and how company insiders will soon be able to sell shares if they choose to, according to a report from The Los Angeles Times.

On Aug. 16, some 271 million shares will be available for trading. Approximately 243 million shares will become available for trading in a several week period in October and November, as well.

Then on Nov. 14, over 1.2 billion shares will be available for trading. Reuters estimates the company could see some 1.88 billion more shares available for trading by the end of 2012. But just because insiders can sell their shares doesn’t mean they will – at least the company hopes so.

Other causes cited for the decline are lingering questions about future company growth and a few key executives (Katie Mitic and Ethan Beard) leaving the company. Facebook saw revenue growth of 32 percent in the recent quarter, compared to over 100 percent in revenue growth during the same quarter in the prior year.

“Unless Facebook can do something to improve its growth rate, there seems little obvious reason for it to trade at a gigantic premium to Google, which is basically in the same market and growing faster despite its much larger size,” according to a recent report in Forbes by Eric Savitz. “The bottom is out there, but I’m not convinced this is it.”

One blogger commented on Forbes that “Facebook is in effect done as a[n] advertising platform behemoth. It no longer provides real value as a social network either. People are moving in droves to Pinterest, Fab and other more trendy sites because of the boredom and in your face advertising in new streams and elsewhere on site that keeps getting more invasive.”

In some other troubling news, Facebook reported more than 83 million Facebook accounts are duplicates or fakes. 

Things could change for the company if it could come up with successful methods for finding ways to take advantage of the users who go onto Facebook via mobile devices. More generally, the company needs to find ways it can profit from its products.

Other suggestions reported by USA Today to get Facebook back on track are making CEO Mark Zuckerberg chief technical officer. Put in a CEO with more Wall Street experience. Make mobile access – as opposed to Web access – a top priority for the company. Facebook also needs to make fewer promises to investors but be clear about the market it is trying to reach, the potential revenue for the market, and what it will do to gain that market.

“Realistically, the company needs to deliver proven results by the time its fiscal Q4 quarter and its fiscal year come to a close,” TechZone360’s Tony Rizzo said in a report on TechZone360. “Six months from now the story needs to have a happy ending – if it doesn’t Facebook will survive but it may lose its now dominant position.”

Facebook still has its proponents. One blogger on Forbes predicts the company “will easily be worth 200-300 billion in five years.”

But there are related concerns for the present. For example, the government of California may not receive “hundreds of millions of dollars” in revenue it anticipated from capital gains taxes because of Facebook performance.