Cool Demo @ the Apple Store
When I got my first iPhone, 3G in Canada from Rogers there were no accessories available that day at the location I bought it from (who's kidding who, there were enough bigger problems that day than a lack of accessories, remember?) Being a bit of a klutz and recognizing the obvious glass face on my new iPhone, I went to the closest Apple store to buy a case, or at the very least a screen protector.
The Apple store associate, asked me why I felt I needed one, and I proceeded to say, that I always had put my previous phone in my pocket with my keys, and it had got scratched and I was concerned about the glass on my iPhone getting marred by my keys.
The Apple associate asked me for my iPhone, and my keys, and with a mischievous glint in her eye, proceeded to "key" the front of my brand new, minutes old, waited in line for ever iPhone...I nearly died. "Take a look," she said, and held up my iPhone with nary a scratch!!!!
To this day, I've left a screen protector off my iPhone, kept it in my pocket, at all times, and 2 years laster, not a scratch on the glass at all. (The back black plastic parts are nicely protected by my Vaja ivolution Grip)