... come on, say it. You know you want to.
I decided while at the OSU game Saturday that more people on average respond to O-H than say excuse me after bumping into someone or bless you after someone sneezed or thank you when someone holds the door for them.
While my research is far from official, my best guess is that (around work anyway) roughly 28% of people say thank you, excuse me, etc. in appropriate situations. I'm going to guesstimate that nearly 86% would respond 'I-O' when prompted with 'O-H'.
Granted, I'm in Ohio, so my results might be a little skewed. I plan to continue my research while on vacation next week, so if a crazy woman yells 'O-H' at you while at a Pennsylvania turnpike rest stop, you'll know why.