The real reason why you're not supposed to use God's name is that, in the Jewish mythology, doing so would summoned Him into your presence. If you call forth God, you'd better have a damn good reason! After all, He is a busy deity, what with the smiting and all.
Actually, you CAN summon forth God, provided you actually have a good reason. Like, wanting to ask him to kill your enemies, for example.
This is why the ancient Jews would never utter the name of--you know who. Even more sever was to (gasp) write it down. For this reason, they would leave some of the letters of his name out, just to be safe. To be even safer still, they would call Him by the general term, "God," rather than by his given (?) name.