it's not HP's fault, since i believe HP doesn't produce those screens themselves.
i once had a 17" tft from philips, and in the manual i could find a table with the exact amounts of dead pixels that are considered "minor" flaws.
there's also a difference between 5 individual pixels, for example, and 5 pixels next to each other.
then there's sub-pixel flaws, which seem to be even more minor (minorer?
).
like i said, it's not a ppc thing, any device with a tft-screen has some sort of "lee-way" in regards of pixel functionality. don't blame HP, DELL, etc. blame the screen producers.