Originally posted by Foxxxen
It's one thing to adjust to the fact that we are short in a tourney, and another to say it has greater expectation than playing full stack. I'm not sure I fully understand your reasoning, so if you would elaborate or illustrate with a couple of examples that would be great.
To clarify, I am indeed saying that starting a hand with a stack of 4 BB can mean that you expect to gain more chips than if you start with 12 BB, not just that you should adjust to having a shorter stack. One source of the advantage is that short stacks have an intrinsic advantage from the rules of poker. Another is that having a short stack adds complexity which can provoke errors from players who are not used to the situations which arise.
If you have 4 BB, then you can pretend that all of your opponents have at most 4 BB. You can optimize your play for this, playing more hands (e.g., 3-betting after a raise) which would suffer from reverse implied odds, and fewer hands which rely on implied odds. Your opponents can't simultaneously play the right ranges of hands for 4 BB and for 12 BB, and this gives you an advantage.
When you are close to all-in, you can sometimes make a defensive push. Let us suppose that it is the turn, you have 2 BB left, and your opponent bets (or raises you 1 BB). You feel that your opponent sometimes has a mediocre hand (perhaps with a few outs), and sometimes has a strong hand, but rarely has complete air, and that you are clearly behind his range. With many hands that you would ordinarily call on the turn, and then call on the river, you should raise all-in on the turn. This takes the option of checking the river away from your opponent, while you pay off better hands the same amount. When you catch your opponent with a mediocre hand, he either has to fold on the turn getting great pot odds, or else you get full value. This is like a raise for a free showdown with no risk of getting 3-bet.
In tournaments, many players do not adjust their flop hand evaluations properly. You normally give up with some hands on the flop due to the threat of later bets. However, if the effective stack depth does not allow a full bet on the turn and river, then calling down may be significantly cheaper, and you may be able to call on the flop with much weaker hands than normal.
I don't think this is worth a lot in cash games, but it is interesting that starting the hand with under 12 BB is not a mistake in theory, even though many poker players incorrectly believe that it is.