24/7 Wall St.

Amidst the excitement about Facebook Inc.’s (NASDAQ: FB) nearly 50% revenue growth rate and its successful, accelerating movement into mobile, something is lost. Facebook is still a very small company. Therein lies most of the risk of its future.

Facebook’s fourth-quarter revenue was $3.9 billion, up 49%. It made $701 million dollars on that. Revenue for the year was $12.5 billion, up 56%. Net income for the year was $2.9 billion.

What does Facebook want Wall Street to look at? Among other things, that mobile advertising was 69% of revenue in the fourth quarter. Also, monthly active users rose to 1.39 billion as of the end of last year. The company probably would like investors to ignore that the monthly active user base rise at the end of last year was only 13% better than at the same time in 2013.

Based on revenue, Facebook is about the same size as Whole Foods Market Inc. (NYSE: WFM). Almost anyone would argue that Whole Foods is a slow-growing business. Therefore, it does not have nearly the potential that Facebook does. But neither company has even a modest fraction of the revenue the largest public companies do, which runs into the tens if not hundreds of billions of dollars.

ALSO READ: Facebook Boosts Global Economy by $227 Billion

Given its very modest revenue size, it has been pointed out often that its $210 billion valuation makes it the 12th largest among U.S. public companies. That puts it ahead of JPMorgan Chase & Co. (NYSE: JPM), Pfizer Inc. (NYSE: PFE) and Verizon Communications Inc. (NYSE: VZ). Facebook’s market cap is two-thirds the size of Google Inc.’s (NASDAQ: GOOGL).

Facebook’s revenue needs to grow tenfold to “grow into” its market cap, if revenue has any role in market value. At $125 billion, Facebook’s revenue likely will not be growing much. At some point the value of its billion or more users falls off, unless the revenue generated by each does more than skyrocket over the next few years. With active user growth slowing, revenue per user has to spike for revenue to continue to rise at a remarkable pace.

Much of this analysis is old, but worth repeating. The value of Facebook could be undercut rapidly, unless it can sustain a 50% growth rate. With each quarter, the will become harder. It happens that way with nearly every corporation — unless that company is Apple Inc. (NASDAQ: AAPL).

ALSO READ: 3 Top Internet Stocks to Buy for Possible Big 2015 Gains