So, funny I was thinking about this stuff this morning...
I don't know if I every really BELEIVED in Santa and I don't think the realization that Santa wasn't "real" was any big trauma.
I had two different sets of Christmas traditions, with each happening every other year. In Virginia, with my mom, there was the big to do on Christmas morning with tree, presents (including several from Santa) and a big stocking stuffed with so much stuff it had to be magic (my mom had real talent in the Christmas Stocking and Easter Basket stuffing skills) Then we drove out to Richmond to my maternal Grandparents where "Santa" always left a couple extra for me. In Connecticut, the big to do was on Christmas Eve, dinner, presents (during which I was center of attention for MANY years) and midnight service. Christmas morning seemed to be an afterthought and my paternal Grandma seemed to just go through the motions (dinky stocking, a couple cheap presents) before shooing me out so she could clean before her Christmas Day open house party (I remember opening my Santa presents in the foyer once because she wanted to vacuum the living room)
I honestly think the only reason there was Santa presents in CT was because my mom said so.
So, the inconsistency really nailed the coffin in the Santa myth pretty early.
However, like I said, I don't think there was any real trauma about it. It was a fun game with the Virginia family and EVERYONE played along, even when the only stockings at my Grandparents house were stuff for the cats. I think I just accepted it as such and it was fun. It's not like I was hurting for the lack in CT either. I was spoiled rotten up there, being the only child on that side of the family for most of my childhood with grandparents and aunts just doting on me.
I will say that there was no stress on the naughty/nice thing. Christmas just meant presents from a fat guy in a red suit, lots of sugar and pretty sparkly things.
Now, the Easter Bunny, OTOH, my mom had complete control over that holiday and I believed in that one for a long time. Too the point were I was inconsolable one night before Easter because Northwest went to chase something in the woods and Dad made a joke about him chasing off the Easter Bunny. Bad Scene.