Facebook shares are tanking as analysts doubt the Company’s ability to generate revenue to justify their share value.Late on Saturday Australian time, Facebook shares were down nearly 5 percent to $18.15. This is less than half the stock’s initial trading price of $38.

The Facbook stock plunge comes as several companies look to take Facebook on with new social network sites.

The company, which now has a market capitalization of $40.89 billion as opposed to the $100 billion when they floated in July 2012, has also seen several senior executives dump their stock in recent weeks.

Market research firm EMarketer estimates that, while robust growth rates will continue for the foreseeable future, advertising revenues at Facebook will not fly as predicted.

Among the people who have dumped stock is company’s earliest backer, Peter Thiel, and Facebook co-founder Dustin Moskovitz.