(Reuters) - Facebook Inc FB.O shares slid on Thursday, as investors shrugged off strong quarterly results and worried about the cost of the company's decision to spend more on preventing misuse of the world's biggest social media network.

FILE PHOTO: Facebook logo is seen at a start-up companies gathering at Paris' Station F in Paris, France on January 17, 2017. REUTERS/Philippe Wojazer/File Photo

Shares of the company were down as much as 2.6 percent at $177.82 in morning trading on Thursday, making it the biggest drag on the S&P 500 and Nasdaq.

The stock is up more than 50 percent this year and it hit a record high in regular trading on Wednesday, tempting investors who have profited from its run higher to cash in their gains.

“Results were good for Facebook, but the forward spending is a concern,” Kim Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh said.

The social media giant reported a 79 percent surge in quarterly profit on Wednesday and revenues were up nearly 50 percent, showing just how insulated Facebook’s business remains from the political criticism of the company which has dominated recent months.

At least 13 brokerages raised their price target on shares in the world’s largest social network following Wednesday’s quarterly results, with RBC Capital Markets making the most bullish move and raising its target by $35 to $230. The median price target was $208.

“Yes, we take foreign meddling in U.S. elections very seriously. Call it what it is – political warfare. And countering will – and should – raise the cost of doing business for FB,” RBC Capital analyst Mark Mahaney said.

“But that business is inherently extremely impressive.”

Facebook has faced criticism in Washington over its failure to prevent Russian operatives from using it for election meddling and Chief Executive Mark Zuckerberg said he would increase spending on security and double the 10,000 staff who review content on the network in response.

The company said the spending would hit profits, with expenses overall expected to grow by between 45 and 60 percent next year.

Of the four high-performing technology stocks beloved of investors this year, Facebook is a close second behind Netflix in performance, reflecting growing confidence in its model and power with advertisers.

The company continues to increase its more than 2 billion regular user base. Its two messaging services, Messenger and WhatsApp, have more than 1 billion users each and the average price per ad rose 35 percent in the third quarter, Wednesday’s results showed.

Barclays analyst Ross Sandler said the company “should have plenty of runway for years to come – and remains a core holding for any internet investor.”