Facebook drives Smartphone’s usage and thus Smartphone might drives Facebook down too.

Seriously Facebook's 40% plunge from its initial-public-offering price of $38 in May has millions of investors asking a single question: Is the stock a buy? The short answer is "No." After a recent rally, to $23 from a low of $17.55, the stock trades at high multiples of both sales and earnings, even as uncertainty about the outlook for its business grows.

The rapid shift in Facebook's user base to mobile platforms—more than half of users now access the site on smartphones and tablets—appears to have caught the company by surprise. Facebook (ticker: FB) founder and CEO Mark Zuckerberg must find a way to monetize its mobile traffic because usage on traditional PCs, where the company makes virtually all of its money, is declining in its large and established markets. That trend isn't likely to change.

There is this facts that, Smartphone industries wouldn’t propelled that much if its weren’t for Facebook, Facebook drives most of the Mobile traffic around the world with its staggering legions of users, with that we can assumes “Facebook drives Smartphone’s usage and thus Smartphone might drives Facebook down” too.

Social service giants from its initial startup in Zuckerberg’s dorm room in 2004 has mind blowing pace in gaining users adaptability in web platform, till 2007 Apple kick start the mobile world with their revolutionizing first iPhone, and since then Facebook seeing most of its users migrating into mobile platform at a significant pace, thus moving massive of Facebook main revenues in web platform into “Ad Free” zone .

Success in mobile is no sure thing. The small screens on these devices don't give Facebook much room to configure ads without alienating users. And the way that mobile users access Facebook, through applications on iPhones, iPads, and Android devices, may diminish the time users spend at the Website while handing greater power to Apple (AAPL) and Google (GOOG), which dominate the apps business.

What are the shares worth? Perhaps only $15? ( as mentioned by Barron’s ) Or lower?. That would be roughly 24 times projected 2013 profit and six times estimated 2013 revenue of $6 billion, still no bargain price. Wall Street's consensus estimate for 2013 shows earnings rising 31%, to 63 cents a share.

That pro forma number is generous because it ignores Facebook's very significant stock-based compensation. The company has been issuing gobs of restricted stock to engineers and other key employees in the hot Silicon Valley job market to prevent them from being lured away to the next hot tech start-up—the next Facebook.

Facebook issued $1.4 billion of restricted stock in 2011, or nearly $500,000 per employee. So far this year, the company has doled out $1 billion of restricted stock. Facebook's reported stock-based compensation expense—based on the amortization of several years of stock grants—could total 20 cents a share next year. Subtract that from the 2013 consensus earnings number, and the shares trade at 50 times earnings. At $15 they would still be valued at a rich 35 times earnings.

TECHNOLOGY IS THE ONLY MAJOR industry where companies routinely encourage analysts to ignore stock-based compensation expense—and most comply. This dubious approach to calculating profits is based on the idea that only cash expenses matter. That's a fiction, pure and simple. As Warren Buffett has said, companies could take this to the extreme, pay all their expenses in stock and claim to have no costs.

Facebook's restricted-stock grant was so large last year that it may have exceeded its cash compensation costs. CEO Mark Zuckerberg seems to have a cavalier attitude, saying in a recent interview that "the way we do compensation is that we translate the amount of cash that we want to give you into shares" and give more stock to employees as the price declines.