A friend of mine and I made our second (first daylight) attempt at a stash NW of Chicago today. Turns out we had a few wrong numbers in our GPS, but we found something cooler - another geocacher. We had just took left the truck and realized we had no pen, so we turned around to go back and get one. We were leaving the second time we a guy hollers "hey, guys" from his car. We had no clue what he was talking about. Then he reaches into his car and pulls out his own GPS. Then it clicked. It was a very cool experience.
I always figured eventually I'd see someone in the same place at the same time, but not on the second trip out.