I wonder if the second guy offered higher...
When I sell, the first agreed sale is golden. Anyone else who is negotiating with me (at any stage other than "deal"), gets put onto a list ("if the falls through, you're second" "I've got two guys ahead of you", etc).
I hadn't given much thought to why the EMT rule, until it was explained above - good explanation, makes good sense. I'm glad I have been working with the "first deal wins" - to prevent that mad rush to get EMTs done. Mind - if I strike a deal with someone, and that EMT can't or doesn't happen instantly, I'll give him a drop-dead time (24 hours?), then go on to the next "deal". But there is plenty of communication with the first deal before that goes south.