As planned, we took advantage of being at the Apple Expo to perform a live test. The goal was to evaluate the resistance of the glass plate sitting in front of the LCD panel of an iMac 24" Alu:
The glass plate turned out to be stronger than expected, and could resist to quite substantial shock despite its thickness.
However, it is NOT a "securite" type of glass, and when it brake, we obtained sharp glass pieces. Nevertheless, your iMac 24" will have to fall to potentially have the glass plate to break.
[translation by Linathael]