What does the PG in PG-13 mean?

This morning on a box of sugary kids' cereal, I noticed an ad for Spider-Man 3. It got me thinking: why do PG-13 movies get advertised to little kids? I mean, it's one thing to have ads on television, but when they put toys in Happy Meals or cereal, which you know no self-respecting 13 year old is going to admit to eating, they have to know who the target audience is.

And that got me thinking that they wouldn't waste money on advertising and promotion if they knew it wouldn't pay off. Which means that there are parents who let their six-to-twelve year olds go see these movies. And I just don't get that. My oldest son will be 11 in July, and even though I would love to share some of my favorite movies with him, I don't. Movies like the first Spider-Man, while fun, are also very scary, and have a fair amount of violence. Even my beloved Pirates is just too intense for him (though in its favor there is no bad language).

I know that a lot of the movies I watched as a child and teenager were rated PG, when today they'd probably be PG-13. But I was forbidden to see R movies, even on video. And that is as it should be. Why are people so anxious for their kids to grow up? I knew someone a few years ago who let her five-year-old watch the Indiana Jones movies and Harry Potter movies. My son still hasn't seen those.

Maybe I'm just over-protective. I won't argue that I'm not. But I think that the world could benefit from a lot more over-protectiveness and a lot less 8-year-olds watching people kill each other.