TI'd be inclined to agree... if I didn't know the following story. I knew a woman who was shooting a wedding with her DSLR, when all the sudden in the middle of it, it just craps out on her, and she had no backup.
This isn't all that uncommon - the few pro photographers I'm acquainted with all have some sort of similar first-hand story. Digital cameras are more complex than film cameras, so there's more to go wrong.
I will note if you're shooting the wedding with an assistant (as a lot of pros do), the assistant's camera can be the backup if yours craps out. But you HAVE to have a second body available, one way or the other. There's just no second chance when it comes to a wedding.