Dude, I support you. I used to try with and without case. You could see my iPhone sometimes naked, sometimes with protection. I have had all four generations of iPhone and I have to say; well, for the first three, it does not matter if you carry around a case, but especially for the fourth generation, do not! You will ruin the sexy look/aesthetic/feel of it. Just apply screen protector - that's it. I did not even put any on my phone, I believe the glass is scratch resistant enough (not scratch proof though, stay alert). Just make sure do not drop it from the height of 2-3 m
However what concerns me most is not the glass cover, but the stainless steel band. In my opinion it is more scratch prone than the front and back surface. I just dropped my phone from my bed (30cm high only, I am serious) but yet one little and hardly noticeable scuff appeared. Not an eye-sore, and I do not really mind about it, but yes, it proves that the band is not so tough as advertised.
If you read around, there are people claiming that the Apple bumpers scratched their metal bands. It was not the bumper but the sand or debris that got inside the case that rubbed the phone. Therefore, either you clean your case everyday (to make sure no debris/sand/dust got inside) or you carry your phone naked, but be double careful.
One more thing: if you leave your phone caseless, anyone who look at it will know it is iPhone 4. So kind of more show-off, do you think so?