As someone who's been diagnosed and heavily medicated for ADD, I think I can say that ADD is a symptom of crappy schooling, not mental deficiency. Standardization, overly-large classes, stupid criteria... give me a reason to pay attention in the first place.
I can focus perfectly well on something that actually interests me, and the medication didn't help me focus on anything I didn't care about. Adults are prescribing amphetamines to children because we were bored with the things they try to cram our heads full of.
EDIT: To cover my own ass, I'd like to point out that I'm painting with a broad brush, here. Of course there are going to be genuine cases, but as far as I'm concerned, ADD is a moneypit for the pharmaceutical industry, and we all know how much they and the government love to finger-fuck. That means that nobody with the power of oversight is going to step in and say "hey, really, guys? Everybody has it, now?", because the government gets huge cut of the profits. God bless 'Murrika.