Five executives have left Facebook in the past four months, including co-founder Dustin Moskovitz, who is leaving to start another social network that will focus on business. The other four departures were product vice president Matt Cohler, chief technology officer Adam D’Angelo, engineering manager Jeff Hammerbacher and platform director Ben Ling. Top engineer Justin Rosenstein will also leave with Moskovitz.

On August 5, Facebook said it had designed a “one-time programme to enable employees to realize some liquidity.” It has since been announced that the programme will begin on November 1. The plan will allow Facebook employees to sell up to 20% of their vested stock options at a price that values the company at $4bn, according to information seen by Breakingviews.com and technology industry news reports.