LaCie, Lite On, Mitac, NEC-Mitsubishi, Neovo, Packard Bell, Philips
Lite On is the only manufacturer to claim that they will take back a panel with a single, solitary, defective pixel. It remains to be seen whether the superstores will follow suit. Sadly, it seems that this is not always the case: some of them apply a rule that requires three.
NEC has taken an original stance, which, fortunately, is to the advantage of users. The official line is that the manufacturer complies with the ISO 113406-2 standard. But they are aware of the standard's limits, and have thus decided to stretch it a bit and apply the same rule to 15" and 17" alike. And that's a good thing, too!
Neovo, CTX and Relisys all refused to reply. See comments on CTX and Relisys.
Packard Bell had yet another rule, which is vertically aligned pixels.
Then there is the Philips "zero-lit-pixel defect" guarantee, which covers the lack of lit or colored pixels, but not unlit ones. Still, unlit ones are not nearly so bothersome. So, praise to Philips for this initiative, even if they really should extend it to their entire range.