What's the biggest lie you were conditioned with? I think I was 5 or 6 when my grandmother passed. One day around that time I was in the front seat of the truck with my mother. I wondered what the "hazard light" button was. She told me that's what you push to "make us fly straight up into the sky so we can go visit grandma" .. or something. Something came up, I think, and I was just left sitting there pondering that for a good few minutes. Why couldn't it? Planes fly, they both have engines and operate in ways that are just as good as magical to the understanding of a 6 year old. I ended up believing that for a solid half-decade before around 10 or so I was with friends and we were stuck in traffic where everyone was complaining. I suggested "why don't we just push the fly button" .. after I explained it to them, the adults smiled at me, and the kids there just started laughing. Man. Come to think of it I turned out alright in comparison.
Fortunately my father always chose to give me alternate perspectives, a healthy dose of reality, I suppose. To the chagrin of my mother, we'd always watch "America's Most Wanted" every Sunday at 9. I'd always be coming up with "what would I do if..." scenarios as a result.
I disagree with the idea of Santa Claus being akin to a "cruel, counterproductive lie" though. Depending on the circumstance, the occasional glimmer of magic and wonder in an otherwise mundane world can make for happy times, at least early on. Besides, depending on where you live, the possibility of a strange old man breaking into your house and attempting to offer you presents in exchange for you to "be a good boy and listen" is very real. Holidays are weird like that. On Halloween, you dress up your kids in shiny outfits and send them off to stranger's homes unsupervised with the implied rule of eating anything they wish to give you. On Easter, if you happen to be in the woods on an Easter Egg hunt, if you ever run into a strange man in a bunny costume you "won" and need to follow him to wherever he may lead you. Etc. Jeez what a world.