If there is a reason for this, it should be explained somewhere easy to find
I signed up via PayPal yesterday for myself and my wife.
I am trying to register for sessions -- it would not let me.
Instead, it wants to have me sign up for DrupalCamp Again and Pay for it again.
Since PayPal has already verified the charge directly to me, I don't think so. If anything, I would have to contact them and say that the product I paid for was not being delivered!
Not a good start...