OK, I'll bite. Why does quality need to be 100%? It isn't for any other device this size at sub-VGA resolutions. Nintendo DS: stuck pixels. Sony PSP: infamous for stuck pixels (and Sony's policy, no returns unless you have like 8 or more stuck pixels).
I think it depends on how you classify "need".
I've found people on MacRumors to be some of the most unreasonable consumers ever. That said, dead / stuck pixels really are irritating, and shouldn't be a problem on an iPhone-sized LCD.
Personally, my DS has 0 stuck pixels (as did my first iPhone, as do my iPod, GPS, and other sub-VGA devices).
Pretty much every LCD manufacturing process ends up with some units with stuck pixels, it's not an indication of poor manufacturing conditions, it's just the way the things work.
Yes and no. This was mostly true about ten years ago, but manufacturing processes have improved substantially since color LCD's reached critical mass, and continue to do so.
The notion that all LCD's are inherently flawed and that a consumer should be happy they didn't get a unit that was more flawed than another is retail manager B.S.
One thing to note is that sometimes when a device comes with stuck pixels out of the box, those pixels fix themselves after a few days. So unless you've got a few of the suckers, might be worth just waiting a week or two, and then if they are still there, taking it back. I guarantee you you'll have a lot less hassle swapping the device in a couple weeks.
I'd go out on a limb and argue both points.
Yes, some pixels really do seem to get their act together and start acting normally. Other times, bad pixels are indicative of a larger problem, and you'll see the problem spread like a cancer.
As far as waiting to return the phone, I'd think holding out a few weeks gives AT&T or the Apple Store more ammunition to blame you for abuse. Not to mention that the Apple Store's return policy is 14 days.