Wishbone: I strongly recommend that you do
not play ME2 without having played ME1 first. You will understand absolutely nothing of the story if you do. You will also have none of the connection to many of the characters that ME2 expects you to have. In short, your experience of the game won't be nearly as good, and most likely extremely confusing.
Gundato: While I do suggest playing ME first, I have to call that post a load of crap :p
The only thing you will be missing out on is backstory with two of your party members, neither of which had a lot of development in the first game (and said development is explained when you first talk to them).
Nah, the real reason to play ME1 is to further enjoy things, and to make your own Shepard.
Actually, by not playing ME1 first, he loses out on importing, which is a big deal considering how much it can change your game. The default Shep loses out on many bonus quests and has made many questionable choices. It is possible to get downloads of saves that people have made of certain types of playthroughs, so he can skip it if he's willing to look around and pick them up instead, though he may not know the choices they refer to. Without importing, he will miss out on some aspects of the game.