It looks as if it has happened again - we now have reports that an unfinished build of Gears of War 3 turned up on torrent sites this weekend. In a statement to VG247, Microsoft say that they are "working closely with our security teams and law enforcement to address the situation." They were also quick to point out that whatever is in that torrent is "not from a final build and is not representative of what fans will enjoy when the game launches worldwide on September 20, 2011."
The code leaked is not something anyone can play either, as it will only run on a debug Xbox 360 - something not a lot of people (relatively speaking) have access to.