This Wired article
talks a bit about hackers getting an emulator running on a PSP that allows them to play old versions of Mario World.
Sounds kind of cool, but unfortunately not everyone will be able to run it:
There is one catch -- so far, the hackers have only found a way around the security of the original firmware that was installed on the first batch of Japanese PSP systems. Later units, including every one released in the United States, contain version 1.5 of the firmware, which tightens up security.
When it became available, Sony made the version 1.5 upgrade available to users via download, encouraging them to update their systems. Those who did not upgrade are the only PSP users who can run the emulator software, as well as all other PSP "home-brew" applications such as original, user-created games.
I have to say, I don't get it. I understand why a company like Sony would want to do certain things, like protect their hardware from cheap clones, protect their software from piracy, protect their movies from being pirated, etc etc, but why would you want to discourage independent development to take place on your product? Encouraging development can only help your hardware sell by creating niche communities and fan bases outside of your normal user base. People are going to want to do this stuff anyway (especially with mobile devices), so why not acknowledge that and profit by it?