Now that Christmas is over for most people (except for my Ruskie and orthodox friends and people who know about epiphany), its time for an unpopular opinion.
From my perhaps overly cynical point of view, Santa teaches kids two things:
1. Material possessions are what really matters in life, and
2. Some kids deserve better things than others.
The first point is pretty obvious-- as a culture, we tend to frame Christmas as a secular holiday about getting stuff. Not even about giving stuff, but about getting stuff. And even the hard core super Christians tend to shape their holiday around the stuff aspect. Especially for kids, what you get is the most important part of Christmas-- they compare their gifts with their friends in great detail-- and that ties directly to the first point.
Because up to a certain age, kids believe in Santa. They believe there is this magical man who evaluates how naughty and nice kids are, and who gives kids presents based on their niceness, which, since abstract concepts, even easy ones, tend to be difficult for very younguns, is often equated with worth.
So you get a classroom, and a bunch of kids who don't really understand class differences start comparing presents and some major disparities are going to show up. Santa brings one kid a bike, an iPad, the newest games, and some cool clothes. Santa brings another kid some less cool clothes and some candy. They both asked Santa for a bike and an iPad, so why did Santa bring them less things? They don't know that Santa is really mom and dad, so they go home feeling sad, and like they must secretly be "bad" kids after all. That sucks.
The anticipation of Santa is great, and the joy kids get opening presents is great, but I know people who felt bad because Santa didn't deliver like he did for other kids. And sure, there's probably an element of greed there, but the question of character, and worth lingers with kids too, and on the societal level, its pretty messed up.
I don't know whether we're going to tell our hypothetical future kids about Santa. Based on our careers, we won't have to worry about our kids being in the sad group for financial reasons, and it kind of sucks for kids to get left out of the whole thing. But I still really have come to dislike the whole Santa concept.