My parents never 'lied' to me or my sisters about it. They played along, and if we asked if he really existed, they answered with non-conmittal answers like 'what do you think?' When we were little, we answered, 'we believe he exists' and went on with what we were doing. When we grew older, the answer became 'I don't know', or 'he can't exist'. I felt proud that I discovered the 'adult' secret about santa all by myself, without being told, and never felt anything collapsing like some people mention. I'm very glad I was never lied to, so I feel that my parents aproach to the situation is a very good one.