I have a lot to say about this topic, but I'll try not to keep all of you too long.
WDW is NOT one of those typical family vacations...it's hard on the parents and the kids. And to top it off, it's a hundred degrees, the parks are packed, and the lines are intense. All of these factors conbined can lead to a breakdown of patience, and a loss of decorum.
Parents are almost expected by their own peers to make the experience "magical..." which usually means spending a lot of money, which is a concept that kids don't grasp. So, in my opinion, a lot of parents start off having attitudes which are...dare I say...anti-Disney.
I think one of my main problems with bringing infants is that chances are, when they are teenagers, they probably won't remember any portion of their vacation to begin with. It's tough for both the parents and the kids. I don't know about you, but I would die in this heat having to carry around a group of exhausted kids.
My advice to a lot of the parents out there is to evaluate your childrens' maturity levels. If your five year old can't make it through Toys R Us without having a tantrum of epic proportions, Disney will be a nightmare, filled with a lot of "I WANT IT NOOOOWWWWWS." Take your kids when they are a bit older, to avoid the whining, and if you want your kids to actually remember the magic.
WDW is my favorite place in the entire world, and most definitely a right of passage for kids, but a lot of other factors should be considered when making a WDW vacation.