I've thought a lot about this question and have sort of swung back and forth in the way I deal with giving my kids information. I live in a really academic area. My friends are all really well educated and a lot of them are academics professionally. I've been most comfortable in the past meeting the world on those terms. When I first became a mother , I was really gung-ho about being open and honest with my kids. Correct terminology for body parts, planning to play the 'Santa' thing as a nice little tradition that parents do for their kids, encouraging questions about things that I found politically pressing like conservation.
But our path as the kids grew a bit lead us to homeschool and led us to Waldorf. Steiner has pretty strong views about what children ought to be exposed to. He feels that 'reason' answers rather than technical ones will fill their souls early in life so that they are ready later for the details. So, when a child asks "Why does the sun come up?", we should answer, "To keep us warm and to make the good plants grow". He also teaches that for a child under 7, it's important to teach that the world is good. Again, not to trick them, but to build their inner trust so that they can come, in time, to meet evils from a place of sureness.
So, all of that is pretty much opposite what I was doing and what I intended to do. But it kind of resonated for me. It encouraged me to see my kids as children and not as little adults. It reminded me that the way their brains work is not the way my adult brain works; that fears are bigger and I have a responsibility to protect them.
I'm not really sure which way is right, I'm conflicted between wanting to protect my children and let them grow without ugliness, to build their inner strengths in a sheltered place, and wanting for them to be righteous and informed and safe in the way that information can make one safe.
At the moment, I feel that maybe it's less about what kind of information you are giving your child and more about the intent with which the information in given. I just tried to come up with an example of this and failed miserably, so I don't know that I can really explain that point of view. I feel that with information about things that fall under the category of 'advanced' or 'too adult', our own emotional connection to those things is what will come across as the most 'real' to the child and we should take that into account.
Anyway, that's not really an answer, is it? I'm glad you brought it up, though, Meemee, as it's been on my mind.