Done this once with my 3G and it was fine, though I try to use my iPod Classic for that kinda carry on as its somewhat tougher.
I do put my iPhone on a chair beside my bed and was woke up by some noise outside. So I get up, place one knee carrying my weight on the chair while I gawk out the window. Remembering there is something useful under there I quickly pick it up. The bottom of the screen was well distored from being pushed on, I could see text appear under the screen if that makes sense, it slowly faded away but I no longer get up to check for vandals now.