Facebook Inc's stock took a hit on Monday after an article in a financial magazine said it is "still too pricey" despite a sharp decline since its initial public offering (IPO). Though Facebook's stock has plunged since its May IPO, Andrew Bary at Barron's said the stock trades at "high multiples of both sales and earnings, even as uncertainty about the outlook for its business grows". The California-based Facebook's stock fell $2.03, or 8.9 per cent, to close at $20.83 on Monday. The company went public on May 18 at a share price of $38, which it has not matched since. At issue is the shift of Facebook's massive user base to mobile devices. The company is still figuring out how to advertise to people who use their mobile phones and tablet computers to access the social network. Bary said success in the mobile space is "no sure thing" for the company. Mobile ads must fit into much smaller screens, which doesn't give Facebook "much room to configure ads without alienating users," Bary said.