Mr. Moskovitz departs Facebook

Facebook co-founder Dustin Moskovitz has left the company to launch a startup with fellow engineer Justin Rosenstein, who joined Facebook from Google in 2007. The pair plan to build an enterprise-level productivity software package, according to AllFacebook.

Rosenstein says the service will be compatible with, if not derivative of, Facebook. "Our user interface will adopt many of Facebook's conventions, creating a seamless and familiar experience for current Facebook users," he said in a note to friends.

"And if our new development tools turn out to be useful, we hope the Facebook engineering team will come to adopt them."

Facebook has seen a number of executive departures as it adds more seasoned players to its roster: ex-Google exec Sheryl Sandberg, now COO; and VP Mike Schroepfer of Engineering, who joined in July from Mozilla. Schroepfer replaced former Facebook CTO Adam D'Angelo. And last June, Product Management VP Matt Cohler left Facebook to join Benchmark Capital.

A Facebook spokesman says these departures aren't surprising, given the entrepreneurial spirit the company attracted in its infancy. For their part, Moskovitz and Zuckerberg remain close friends.

"Dustin has always had Facebook's best interests at heart and will always be someone I turn to for advice," said CEO Mark Zuckerberg, who worked with Moskovitz and Chris Hughes to launch Facebook five years ago.

Hughes abandoned ship in early 2007 to work for Sen. Barack Obama's new media campaign.