Screen protectors on smartphones

At one time, Verizon used to ship their smartphones with screen protectors. Now, you're on your own and if you're planning on purchasing a screen protector, you can spend anywhere from $2-3 on eBay up to $20 in retail stores. (Guess where I get my screen protectors)

I wish that all smartphones came with a factory-installed screen protector. Sometimes, it's so difficult to install that protector while avoiding small bubbles under the plastic. Over the years, I've seen some novel application methods that have virtually eliminated the chance of getting bubbles.

Do you use a screen protector on your smartphone? I admit that at one time, I had screen protectors on virtually everything that had a touch screen. This includes my PDA, UMPC, tablet, etc. Now, I only use a protector on my smartphone. All my other devices are running "naked" and I've been careful enough that I haven't gotten any scratches (yet).