Linux on Sony hardware has been done before, but not to any great success. Some of you may remember that the PS2 could run a strange version of the open source OS with a bought package that gave you a 40GB HDD, a keyboard and a mouse. However, it did not allow for any functionality of the DVD-ROM because Sony thought you might start using your PS2 to rip off all their games.
There was a lot of noise in the beginning of the PS3's marketing-hype-launch that the console would have Linux pre-loaded, but Sony came to their senses when they realized how much more work that was going to be for them. So we are left to figure this one out for ourselves.