My earliest memory regarding Santa includes knowledge that Santa was not "really" real, but something that we were supposed to pretend. I don't know where or when I picked that up, but I don't think the deception negatively affected me.

On the other hand, my mother is a Methodist Pastor, and the God deception had a much deeper impact on me. I recognized that it was not fiction in the same sense---that my parents believed it, and it was a great source of internal conflict that I couldn't accept God's existence as they could.