I think it's, to a degree anyway, a socialogical thing. The French seem to hug and kiss each other all the time, yet us "Brits" are very reserved.. Sure if I know somebody well, at least a female I'll give a little hug maybe, if it's a guy a handshake will be enough for me.
Anybody I don't know well gets a smile and the regulation hello, maybe a handshake if I'm feeling generous
The states seems to have different reactions all over, The good old New York greeting of "what do you want?" springs to mind..
