With that way of thinking, then why hire a DJ? An IPod loaded with songs can do the same thing. Apparently you have not heard some of the Horror Stories about IPod Weddings!
Best I can tell, an iPod does not announce the wedding party, does not announce and oversee the traditional events, etc. The iPod may have a hard time dragging the bride and groom onto the floor, to do a toast, or a special dance. They may be outside having a smoke -- what does the iPod do?
I think you could get away with an iPod in Canada, because they usually have a family member do MC duties, from what I've heard (disclaimer: I've never been to a wedding in Canada, so I cannot verify this).