My parents--fundamentalist christians--didn't participate in the santa myth, they told us when we first came across santa that it was something lots of people pretended about. The main reason they didn't lie to us about santa--and they explicitly told us this--was that they didn't want us to be disapointed about santa and subsequently decide god was like santa and didn't exist either. Perhaps, that should have been a big hint about the other invisble man, but I was like 5 or 6 at the time and homeschooled.
(Looking back and reading between the lines, I think at least one of my parents was extremely upset when they found out santa wasn't real and vowed never to do such a thing to their own kids.)
I was probably in my 20's by the time I realized that there are people who actually thought santa was real at some point in their life. I had preivously thought that people who claimed to have believed in santa were just continuing the game. Anyway, the joke's on me. Turns out god isn't real. Ha, ha.
I think it's valuable to have an experience of finding out that you're wrong about the world on a very basic level. I don't know that I could actually straight up lie to any hypothetical kids in order to cause such an experience, though.
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.