A parent's desire to hold on to a child's innocence in his early years is normal and necessary. Early childhood is obviously not the right time for them to know certain things. But kids today are exposed to negative influences at earlier and earlier ages, and it is often out of a parent's control.
Age 16 used to be the benchmark for teens. It was the age most could begin to drive, and when given a set of car keys, the influence a parent has on how much of the world their teen experiences changes dramatically. But today, a younger teen has the keys to "drive" on over to some of the seediest places on earth, with the click of a mouse button. The Internet has changed everything.