Cut Throat

I saw a great example of when Implicit Collusion should not apply. I was observing a hand that I folded in which one player was all-in pre-flop. Five people were remaining in a tournament that only paid four. The big blind made a modest (strange) re-raise to against the small blind's call. There was 900 chips in the main pot and 800 chips in the side pot with blinds at 60/120. The flop came JK9 rainbow and both remaining players checked.

The turn was a 6, putting two hearts on the board. The BB had 1,600 chips behind, and the SB had 2,600. If you were the small blind I would encourage you to bet out about 400 chips here. The big blind would likely fold if he had anything less than a pair of Jacks, and would be crazy even to do that. That would risk 400 to win 800, and possibly 1,700 if you win both pots. Knocking the fifth place player out would be beneficial to both players, but betting out would leave him with only 900 chips if he beat you anyway. Meanwhile the big blind would be left with only 1,600 chips after folding and you would have at least 3,400.

Players tend to get angry when you do this to them (especially if they would have KO'd the other player). The big blind probably feels entitled to a check down to try and guarantee money. However, mathematically getting 2:1 odds on a bet here is simply too good to pass up. Only the most stubborn player would continue with the hand once you bet.