Currently, when using Linux on the PS3, Sony blocks access to its RSX graphics unit thanks to its "Hypervisor" chip which can only be got around with Sony's approval. This means that 3D graphics performance in Linux is "bloody awful".
The reason for the block is the fear that 3D games in Linux would be too competitive with the PS3's own games and hence undermine Sony's investment. But Linux fans argue that any games created would likely be homebrew in scale considering the required costs, time and resources of developing a AAA game. One point made is:
"Do they [Sony] think people will code Gears of War 2 at home?"
Hence, Linux supporters have come up with an online petition which will hopefully change Sony's mind.