I was originally from London and people did not normally greet each other there unless they were known to each other. If you were greeted by a stranger one would treat the person with caution, just in case they were on day release from the local mental institution (think Jasper Carrott's 'loony on the bus').

Living in Scarborough, Maine, I am having to learn to drop the reserved ways I was raised in. If I'm walking the dog passersby always say hello and in supermarket queues the cashier or another shopper is likely to start a conversation. Whilst it is nice to have this it is a bit difficult to relax the reserve built up over so many years, but maybe one day I'll get to be the same.