yah I was the same way at first too Lisa when my FI suggested it. And his reasoning was that his friend, aka the MC, would be doing as much if not more work than his actual groomsman b/c its not easy to be an MC! So I agree.
I dont think MC's are common in the US, usually their dj's just mc the wedding, which i thought was so weird at the weddings I went to down south. A good MC can really make a reception!