For an ugly, hairy, smelly man - three feet. For Scarlett Johansson - She could never get close enough. It would be a shame for clothing to come between us.
Personal space is important to me. I want to stretch my arms out to my sides and twist and never touch anyone. I did that at Disney World one time told the people behind me to stop standing so close, explaining they were not going to get to the attraction any sooner. Seriously, it's like no one knows how to behave anymore. I've told people in lines at the pharmacy to back up too.