I went naked for a week, noticed the back logo was getting scratched to high hell. Got a thin black case on the back and a crystal screen protector. I like how it looks better now.
I was naked with my 3G for a year. I got a 3Gs last month, also naked. Right before I was going to return my phone for a defect, I noticed a hairline scratch on my 3Gs screen. I had minor scratches on my previous 3G screen. Neither phones looked "bad" with these micro scratches, but I figured my new 3Gs should be protected.
I bought the Invisible Shield (just to cover the screen) and I'm super happy! Professionally installed, lifetime warranty, in and out service (at my mall). I also bought the Feather case, because it's the only case that I've found that doesn't rise above the glass touchscreen. I hate using an iPhone case where your finger can't slide off the edge of the phone. The Feather has a matte finish, so it doesn't get grimy. Overall, I HIGHLY recommend the Feather / Invisible Shield combo. I enjoy using this method more than my previous naked phones.
http://www.myincipio.com/product/IP..._Slim_Form_Fitted_Case_for_iPhone_3G_3GS.html
http://www.zagg.com/
I have a BSE on my 3GS and I wish I had heard of BSE back when I had my 3G. The BSE is fantastic! It's a slight yellow tint and a small gloss look but it's great.
I tend to see more naked iPhones than those in a case. Maybe it's a British thing. So I feel having a case makes me more unique, I like to spot my phone easily.
Do you leave it lying around in a pile of other iPhones?
Mine's easy to spot, its the one I have on me.