In general, the main way to make people not leak stuff is to make them not _want_ to leak stuff. If, say, it is important to the company that product A not leak

In general, the main way to make people not leak stuff is to make them not _want_ to leak stuff. If, say, it is important to the company that product A not leak, and employees generally want what is important for the company, it probably won't leak. The leak Facebook seems unhappy about basically seems to comprise the CEO saying stupid things to employees. There's probably no way to stop that leaking; no-one has any real interest in keeping it secret. In general when a company irritates its employees, _that_ will almost always leak.