An odd thing happened to me today.
As my friend and I walked onto the 2nd tee (137 yard par 3), we saw an older gentleman - a single-player - on the green. He putted out (without removing the pin), retrieved his ball, and then walked off the right-hand side of the green. That side of the 2nd green is obscured from the tee, as a large pine tree, small hillock, and bunker are all in front of the right-hand side of that green. The path to the 3rd tee is also to the right of the 2nd green.
My playing partner and I watched the old chap putt out and walk to the right of the green, waited a minute or so, and then hit our drives - two good shots - and we started walking to the green to hit our birdie putts.
Someone wasn't rejoicing, though. The single-player, who appeared on the green shouting and waving his putter around. Turned out he was playing two balls, and had played out his first ball before walking to the right fringe of the green to chip his second ball. He must have been walking towards the middle of the green as our tee-shots landed.
I've never "hit into" someone before in over 20 years of playing golf, and was a bit upset by all of this. My playing partner apologized and we all went on our way. Thinking about it afterwards, though, my mood has hardened slightly. I'm inclined to think that you play that second ball at your own risk. If you putt out and look like you're clearing the green, so long as the match behind allows adequate time for the green to clear, there is no more "due diligence" owed on that match's part. I never want to hurt anyone on a golf course, but is it really reasonable to have to anticipate that someone might be playing two balls, and allow extra time for a green to clear, accordingly?