Not naked - it feels too slippery and at risk of taking a dive. Also the power button is too exposed and can easily be pressed when the phone is in a pocket, which will wake it up and waste battery.
I use a cheap gel case, which makes it much grippier to handle while adding minimal bulk. As a bonus there is a little shock protection value, I guess, and the wrap around front lip serves to just keep the screen from touching any flat surface (including pavement, for example) if the phone is placed or falls face down.
My phone is unmarked after more than 16 months.