Andrys Basten has an excellent discussion on the potential 'fragility' issue here:
She was at the launch event and got a 'Kindle Team member' to comment:
In fact, I asked Kindle Team Staffers at the press event about my concern over fragility of a 2nd layer that houses lights over the text display, as I'd read so many reports on mild encounters of the screen with even-soft surfaces that resulted in damage to the lighting mechanism. I mentioned reading information from Nook owners at Barnes and Noble's tech support site.
One Kindle Team member actually gave me an answer (blow me down! as they tend to be so non-commital about everything).
He said that the Paperwhite light-system layer (it has only 4 Led lights) is "strong" and can handle quite a bit. I asked if they had done tests that involved dropping objects onto the screen of a Paperwhite, and he said that they had, and that it had survived all manner of drops onto the surface. I asked him if they'd dropped anything heavy on it, and he said, yes, and mentioned a rather heavy "brass" object and that it survived that too.
And if you go to the Nook forum here, there's been ongoing discussion like the following recent thread:
There, 'dakini' reports;
I'd heard about the light holes and assumed it was probably sensationalist reporting till I got to see one in the US. It had the same light holes. I asked the Nook sales person at that B and N and he said it was caused by a fake fingernail. He added that it happened regularly to their demo models so they stopped replacing them.
Still, I have to assume most people are happy with their Nook STw/G's and haven't had an issue. Apart from Nate's report, and reports about his report, I don't see nearly as many complaints in Nook forums and coming up in Google searches as I'd expect if it were a rampant problem. But only B&N knows for sure.