That's why I pay a bit extra for the Surefire lights, over, say, a Gerber or other cheaper light. Surefire uses thick sapphire coated tempered pyrex glass (similar to what expensive watches use for their crystal, but even thicker and tougher). Unless you're carrying sapphires or diamonds in your pocket it's very tough to scratch it.

It's tough to explain to most people why some of us pay extra for that Benchmade knife or a Surefire light, when there are plenty of other cheaper options out there that do the same thing. But, for me it's those little details, like not scratching the lens when I throw it in my pocket even after 5+ years of daily carry, that make it worth it.