When a product manager at Google told his bosses this year that he was quitting to take a job at Facebook, they offered him a large raise. When he said it was not about the money, they told him he could have a promotion, work in a different area or even start his own company inside Google.

He turned down all the inducements and joined Google’s newest rival.

“Google’s gotten to be a lot bigger and slower-moving of a company,” said the former manager, who would speak only on the condition of anonymity to protect business relationships. “At Facebook, I could see how quickly I could get things done compared to Google.”

Google, which only 12 years ago was a scrappy start-up in a garage, now finds itself viewed in Silicon Valley as the big, lumbering incumbent. Inside the company some of its best engineers are chafing under the growing bureaucracy and are leaving to start or work at smaller, nimbler companies.

Recent departures include low-level engineers, product managers and prominent managers like Lars Rasmussen, who helped create Google Maps and Wave before he left for Facebook, and Omar Hamoui, the founder of AdMob who was vice president for mobile ads at Google and is now looking for his next project. At least 142 of Facebook’s employees came from Google.