Because the PS3 will most likely never see the first Mass Effect, when Mass Effect 2 hit Sony's console developers BioWare had to include an interactive comic to help players make the choices that defined their character's actions.
Xbox 360 and PC players made those choices while actually playing the first Mass Effect, but since that wasn't an option on the PS3, well, the comic had to do. Now that comic is available on the Xbox 360 (for 320 MSP), in case you feel like playing Mass Effect 2 without having to play Mass Effect 1.
Though, really, you should. Answering a glorified Q&A isn't the same as actually making those tough decisions as the game unfolds, and while the first Mass Effect is a little rusty in some places in light of the sequel, it's still an awesome game. And don't worry, you've got plenty of time between now and 2012 to finish both the first and second game. Maybe more than once.
Mass Effect 2: Genesis [Xbox]