Shares of LinkedIn (LNKD) plunged as much as 40 percent at the market open Friday, erasing $10 billion of its market capitalization after announcing weaker-than-expected forward guidance the previous evening.

The social media company reported fourth-quarter earnings and revenue that topped analyst estimates Thursday, but shares in the company tanked in after-hours trading. The slide continued into Friday's regular session, with shares on track for their worst daily performance since going public in 2011, amid a slew of analyst downgrades.

The company said Thursday that it saw adjusted earnings of 94 cents per share on $862 million in revenue in its fourth quarter. Analysts had expected LinkedIn to report earnings of about 78 cents per share on $858 million in revenue, according to a consensus estimate from Thomson Reuters.

For the first quarter, LinkedIn said it expects revenue of about $820 million and non-GAAP earnings of about 55 cents per share. Wall Street had on average expected about $868.3 million in revenue and earnings of 75 cents per share for that quarter, according to StreetAccount.

The company's guidance for first-quarter adjusted EBITDA (earnings before interest, taxes, depreciation and amortization) was about $190 million — analysts had forecast about $213.9 million, according to StreetAccount.

"Our strategy in 2016 will increasingly focus on a narrower set of high value, high impact initiatives with the goal of strengthening and driving leverage across our entire portfolio of businesses," LinkedIn CEO Jeff Weiner said in prepared remarks. "Our roadmap will be supported by greater emphasis on simplicity, prioritization, and ultimate ROI and investment impact."

CFO Steve Sordello said in his remarks that the guidance in part reflects "continued pressure" in international markets from "current global economic conditions."

The company's focus on sponsored content will impact short-term revenue growth in favor of the long term, he added.

"It looks like 2016 will really be a year of refocus and reinvestment, and it seems like investors might be taking a pause on this stock right now," Neil Doshi, analyst at Mizuho Securities, told CNBC's "Fast Money."

In the final quarter of 2015, LinkedIn saw a 34 percent increase in revenue from $643 million in the year-ago period. Adjusted earnings increased 54 percent from 61 cents in Q4 2014.

The company said it ended the fourth quarter with 414 million members, topping average analyst estimates of 409.7 million, according to StreetAccount.

Shares in the professional social network have now fallen about 49.5 percent so far this year, trending worse than the major U.S. indexes.

— With reporting by CNBC's Dominic Chu.

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