I remember at about 8 years old being told by cousins that Santa was not real. I considered it unlikely that something my parents had been telling me would be untrue and argued as such. As it became clear that they were right and there was no Santa, my recollection is I became angry at my parents. I don't have a high degree of trust in these recollections as I also remember believing that I never lied to my parents before the age of 4 years old and I remember being punished for lying when I was telling the truth and being totally outraged. As a parent of three children, it is simply not plausible to me anymore that I actually did not lie to my parents before I was 4. So I generally don't trust a lot of detail of recollections about my parents, lying, and my own personal disapproval or anger.
I've long entertained a dubious regard for the practice of lying to children about the existence of Santa Claus. Parents might claim that it serves to make children's lives more magical and exciting, but as a general rule, children are adequately equipped to create fantasies of their own without their parents' intervention. The two reasons I suspect rest at the bottom line are adherence to tradition, and finding it cute to see one's children believing ridiculous things.
Personally, I considered this to be a rather indecent way to treat one's own children, and have sometimes wondered whether a large proportion of conspiracy theorists owe their origins to the realization that practically all the adults in the country really are conspiring to deceive children for no tangible benefit. However, since I began frequenting this site, I've been exposed to the alternate viewpoint that this realization may be good for developing rationalists, because it provides children with the experience of discovering that they hold beliefs which are wrong and absurd, and that they must reject them.
So, how did the Santa deception affect you personally? How do you think your life might have been different without it? If your parents didn't do it to you, what are your impressions on the experience of not being lied to when most other children are?
Also, I promise to upvote anyone who links to an easy to register for community of conspiracy theorists where they would not be averse to being asked the same question.