"The next system software update for the PlayStation 3 (PS3) system will be released on April 1, 2010 (JST), and will disable the ?Install Other OS? feature that was available on the PS3 systems prior to the current slimmer models, launched in September 2009. This feature enabled users to install an operating system, but due to security concerns, Sony Computer Entertainment will remove the functionality through the 3.21 system software update."
This was a cheap way of getting a Linux box. Sony was losing a little on each PS3, and didn't want to try and make it up on volume.