In an interview with TheStreet, CFO Ebersman said the company ramped up expenses 82% year-over-year and plans to increase them even further as Facebook invests in its people and infrastructure. "Our key issues are investments in our people Facebook ended the quarter with over 4,600 employees and infrastructure," Ebersman said, over the phone. "We are investing in engagement and monetization, and we're showing the results."

One of those initiatives is Gifts. Facebook recently unveiled a way to send gifts to your friends on the platform, most in the $30 and under price range. BMO Capital Markets analyst Daniel Salomon had been expecting Gifts would help Payments revenue, which came in at $256 million for the quarter. "We had been looking to Gifts for help, but management tapped-down expectations, and we have lowered our revenue estimates for it," Salomon noted, in a research report. He downgraded shares to "market perform" with a $32 price target. On the call, Zuckerberg tempered expectations for Gifts, but Salomon noted that any expectations for Gifts to improve would make him get more "proactive" on the stock.

Not all was negative for the quarter, though as Facebook beat estimates, led by higher advertising revenues. The social networking giant reported non-GAAP earnings of 17 cents a share on $1.585 billion in revenue, as the company's top line jumped 40%. Revenue from advertising was up 41% to $1.33 billion, accounting for 84% of total revenue. Mobile revenue represented 23% of advertising revenue in the fourth quarter, up from 14% in the third quarter.

Analysts surveyed by Thomson Reuters expected Facebook to earn 15 cents a share on sales of $1.53 billion in the fourth quarter.

Citi's Doshi noted that the company's mobile revenue run-rate is now $1 billion plus for the year. On the conference call, Sandberg noted that Facebook Exchange (FBX) is not yet available on mobile. "We think FB is showing revenue acceleration due to a mobile pricing tailwind, while other companies, such as Google, are facing mobile pricing headwinds," she said.

Jeffries analyst Brian Pitz believes that FBX could be a huge driver of revenue over the next twelve months. "During 2012, we believe Facebook will generate close to $4B in revenue off its standard display ad units, which appear on the right side of the page (aka the right rail). This is the same inventory that will be sold on FBX. FBX will allow real-time-bidding (RTB), and will also enable retargeting. Retargeting ads will generate CPC/CPA multiples higher than the ads they displace," Pitz wrote in a note. He downgraded Facebook to "hold," taking down the price target to $30 from $32.

Facebook is undoubtedly in heavy investment mode right now, and has tapered expectations for its new initiatives, including FBX, Gifts, Graph Search, etc. While Wall Street is worried about the short term, Zuckerberg and his team are looking at the long term. Considering that the CEO has taken Facebook from being a hang out for college kids in 2004 into a $60+ billion business in 2013, I would say he probably knows what he's doing.

Interested in more on Facebook? See TheStreet Ratings' report card for this stock.

-- Written by Chris Ciaccia in New York

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