I think not using a case makes you separate from others. 19/20 people I see on the bus use a case for their iPhone. Using a case is too bulky for me. I like my device to be as slim as possible. I only have the bestskinever on my phone. I know this is very risky, but oh well.
Most of the time I tend to keep a case off of my phone, but I'll occasionally put one of the few I have on here and there. However, I do always have screen protectors on all sides of my phone.
Using a case from now on, permanently. Otterbox Commuter. My f'in perfect naked phone fell out of my jacket pocket yesterday and now it has minor knicks on the top corner of the antenna band