[Jacques]

My shot at listing the problems caused by this behavior.

1. Checking it down lends to smaller pots and less rake for PokerStars

2. Checking down reduces variance for the players involved since their heads-up pots stay small. This makes it easier to go through a bad streak, less likely to go broke or having to move down or go on tilt.

3. Players not familiar with their behavior will have their read of twin/h@ll distorted. They may expect them to check it down more they actually would against unknown players.

4. Appearance of collusion for the players who notice this, this hurts all winners in the game as well as PokerStars. Some people won't play because of this.

5. After a relatively secret agreement is in place, it is much easier to broaden the agreement to include things much worse, especially when both players are doing bad.

6. It saves energy and time not to have to think against a tough player, not to be underestimated when playing 6-8 tables.