If you want to do something about this, then do it. The phone number is right on the website: 800-345-7669 (800-345-SONY). You can make thousands of posts here, but the only way Sony will know how pissed we are about this is for them to actually hear you! You can press 0 at the menus to talk to a person. Try to convince them that they can still save face by playing this off as an April fools joke.
When I called the person I talked to tried to convince me it is optional. It is not. You get a choice: the ability to play new games that come out, or the ability to use Linux. You don't get both even though that is what they advertised and what you paid for.
Also remind them that this is fraud. They marketed a product and you paid for it under the false pretense that it would do the things they said it would. Sony knows that they are will get sued over this. They look at some bloated "every pirated copy is a lost sale" figure and ignore the few million dollars a loss in court would cost. Even more importantly, if they win, electronics companies will be able to remove core functionality from their devices whenever they want for any reason with minimal if any notice. I truly believe that that is what Sony is after with all of this.
The PS3 is piss poor at everything. The only thing that made it even remotely worth anywhere near the $600 they charged for it was that it did lots of things. Now it is losing half of its functionality. Functionality that we paid for. Remember, the PS3 didn't have any good exclusives its first two years. OtherOS was its huge selling point. I seriously did buy the PS3 for it. I may not use it often because of how bad they gimped it, but I do use it; more than I play the 3 good games for the system in fact.
Lastly, here is a Ken Kuteragi quote on the $600 price tag: "It's probably too cheap ... This is the PS3 price. Expensive, cheap -- we don't want you to think of it in terms of game machines. Because the PS3 is like nothing else." Read that to the people on the phone, ask them what they think about it.