I have always wondered this. My dds have not been christened. I am a godmother to my friend's daughter but see my duties to her more of a way to be there for her as a good friend and someone to confide in if ever she chooses. I am unsure as to my own religious beliefs - bit of an atheist I guess. If my own daughters or goddaughter want to know anything about religion then I am willing to help them understand all sides and feel that they should be able to choose which path they want to take.
I find it very strange that people would go to all the effort to arrange a big do and actually have no beliefs at all. This may sound harsh but I think some people do it more for an excuse to party.