My parents tried to tell my brother and I pretty young that there was no Santa so that we would focus on the meaning of the season. We refused to believe them, so they played along until we got older.
I don't think there's any harm to not letting children believe. It's not scarring them to tell them there's no Santa--my cousins (4, 6, 10 now) were told upfront, they still enjoy Christmas, and they have a great idea about the love that embodies the season. On the other hand, I don't think there's anything wrong with believing in Santa. I think this is totally a parent's call and we shouldn't judge families who choose either way (I'm not saying we are, just saying.)
Also, as a second-grade teacher, I'm pretty sure very few of my kids believe anyway. We didn't really talk about it.
Why do we play with fire?
Why do we run our fingers through the flame?
Why do we leave our hands on the stove, although we know we're in for some pain?
-tick...tick...BOOM!