When I first saw the thread's title, I thought it was a hoax. Yes, Wow.
My Orthodox priest once told me the Pope could never retire and could only be disposed, because a bishop retains his rank, and having a former pope around would create two Popes whose position was of infallible authority. For example, we refer to Met. Jonah, even though he resigned. As evidence of this, my priest, who attended Catholic school, pointed to how old Pope John Paul II was as pope, and even died in the position.
I understand that this contradiction of "simultaneous" popes might be explained away, since one no longer exercizes authority, but it is enough of an issue (Jesus and St Peter didn't "retire"), that retirement is extremely anomalous: especially when his mind still works as well as Pope Benedict's does. Pope Benedict was not a Pope of "change", and this is a big change.
I don't believe the story that the Pope simply retirement due to old age, because that basically doesn't happen, particularly in the case of a conservative Pope like Pope Benedict with a sound mind. The search should begin for the real reason.