Mark Zuckerberg is going to need to find some more pinball machines and rock-climbing walls. The social networking company, known for its many perks that make it a regular on the hottest-places-to-work lists, is increasing headcount at an incredible pace.

Facebook, which reported on Wednesday that sales fell short of estimates, passed the 10,000-employee mark last quarter. With a total of 10,082 at the end of March, Facebook increased headcount by 48 percent compared with the same time last year.

Forty-eight percent is an eye-popping number. Google grew only 12 percent last year. Granted, Google is about five times the size of Facebook, but the online search company actually reduced headcount from the third to fourth quarter, due partly to the closing of its sale of Motorola Mobility to Lenovo.