I think I've seen this topic before by BP or someone...
Anyway, I think that parents should teach their kids what they themselves believe in, because kids do what their parents do anyway, so the parents should explain and educate.
Faith is however individual, and should be treated as such. Parents may want their child to grow up to be anything from agnostic to Sikh, but the faith should come from the child, not enforced by the parents (it would thusly only be "paperfaith" anyway).
And while I think that there should be discussions about spirituality, religion and atheism (and the many options within), I can understand why parents with firm beliefs would not want that. Simplified examples follow:
If I'm Christian, I don't want my children to grow up atheist because I want to meet them in heaven some day/want the best spiritual life for them.
If I'm atheist, I don't want my children to grow up Christian because I think it is false/harmful to them.
If you don't want your children to share your beliefs, then maybe you feel that they are but one of many ways (pluralistic view) or that your way may not be right (agnostic view). Personally, I'd go with the approach that I won't teach my child anything, but when he/she asks, I'll be ready to discuss.
I grew up with a Christian mother and an atheist father, going to church and singing in the church choir until I was 13 and decided that I did not believe. Which obviously was a choice, not just from my parents but also from my friends and their families (Muslims, Jews and a bunch of "I-don't-care"-ists).