or on routine travel from point A to point B, or when you buy coffee/lunch at the same place everyday, etc. — do you ever talk to them, nod hello, smile at them or in any other way acknowledge the fact that you've shared a locale many times before?

Or do you avoid eye contact and pretend that the person sitting or standing next to you is someone you've never seen before and never will again?

Tales of awkward encounters especially welcome.