In a move some PS3 users were hoping was an April Fool's joke, Sony released firmware version 3.21 today for the PS3, the primary (and perhaps sole) function of which is to remove the "Install Other OS" option from the console's System menu. This previously allowed users to install a different operating system — like Linux — to use the PS3 for additional computing tasks.
Sony's standard explanation is that this is a cost-cutting measure. That holds more water when they discussed it as a change with the PS3 Slim when it was announced, but removing it from existing consoles that people have already purchased, systems that aren't even available at retail anymore? That sounds a bit more fishy. Their new explanation is that it's being removed to make the PS3 "a more secure system." Okay, but more secure for whom?
Rumors I overheard around the Slim launch indicated that some users might've been using Linux via the Other OS option to watch pirated movies and run emulators for other consoles and games. As a business model, Sony loses money on the PS3 for the first several years, but makes up the difference on software licensing and sales, which partially explains why they nixed PS2 backward compatibility. This isn't unlike the firmware updates to the PSP that killed homebrew development and emulation on that platform (which were the only reasons I was interested in it in the first place…and is why I still don't own one).
To make it feel like you still have a say in the matter, Sony says the firmware update is entirely optional, with the caveat that you won't be able to use PlayStation Network, chat online, browse the PlayStation Store, or basically have any network functionality unless you accept the update. Further, if you have an existing installation of another OS, it will wipe that portion of your hard drive and reclaim it for the PS3's OS.
It doesn't save Sony money to remove features from an existing console they've already sold, so there must be another reason they're not admitting to. Remember how they removed the firewire port and HDD bay on the PS2, and the parallel (i.e., Gameshark) and serial (i.e., System Link) ports on the PS1 in future iterations of the hardware to save money? That made sense. This would be like them coming to your house and yanking out the ports you already paid for.