When the iPhone 4's screen was shattered, apologists said that the test wasn't valid, and Apple never claimed that the screen was crash-resistant, anyway, only scratch-resistant. Well, it seems that "30 times harder than plastic" is not scratch resistant enough.
In their advertising, Apple says that the iPhone 4's aerospace-grade glass is "chemically strengthened to be 20 times stiffer and 30 times harder than plastic". According to them, "the glass is ultradurable and more scratch resistant than ever".
In his review, Walter Mossberg agreed. He said that he tried to break it and scratch it, and he couldn't do it:
I dropped it several times from a few feet onto a hard surface with no problem, and it acquired no scratches at all in my testing, even though I didn't use a case or coddle it.
But as this photo shows, maybe he didn't try hard enough.
Gdgt editor Ryan Block didn't even try to scratch his, but he got a scratch anyway in normal daily use: Gdgt editor Ryan Block takes this photo of Engadget's J. Topolsky's official Apple review iPhone (thanks metronome49):
Just spotted on the iPhone 4's supposedly nigh-indestructible glass: scratches. Seriously. Not good!