Philosopher - 10:26 pm on Jan 10, 2008 (gmt 0)

I only know mine because I am staring at a piece of mail that has it as I'm writing this. :)

Seriously though, I think the answer is "No". Most of us don't know the +4 at all. It is simply not used for residential mail.

The only time you see the +4 is either on a piece of mail sent from a business or a piece of mail being sent to a business in a pre-addressed envelope.