I was told once that betting big when you have a weak hand or bluffing and betting small on a strong hand is human nature. BS (Barbra Streisand.) Human nature is to shove all your chips in the center when you got a pair of Aces pre-flop or the stone cold nuts and cower behind a rock when your hand misses the flop. The reason some players bet like that, is that it makes sense.

Both myself and an opponent are in on a $1 pot with $24 remaining. I go all-in with nothing. Most of the time (assuming a rational opponent, not always the case at lower limits) this buys me the pot at a profit of probably around 75c (lets say I had a 25% chance of winning showdown on a draw.) However, when I get called it will be by a likely very strong hand, costing around $20. The losses outweigh the benefit of that move. Strong bets will steal pots, particuarly in the short term, but the stronger the bet the higher chance it's long term unprofitable.

Two players are dueling over a $20 pot. Let's say one is a 75% favorite. Hence, if they both checked it down one will average $15 and the other will average $5. However, if one can bet enough to induce the other to fold that fold is worth $5 and $15 respectivly to our players.

If the player leading makes a half pot bet of $10 it puts the other player in a position of paying $10 for their likely share of $7.5 of the new pot. It's in his advantage to fold giving up their $5 share of the original pot. If the bet is called, the better gains $7.5 of value and another round to push their position. If a fold is induced, the better still gains a sure $5. A strong win-win position.

However, lets say the player behind makes a full pot bet of $20 to "steal" the pot. If the player ahead folds, it's a net profit of $15. If he calls, the player behind can expect to lose $30. The bluff needs to work over 66% of the time to be profitable.

However, if one is a 95% favorite it's a very different story. Inducing a fold is only worth $1, a near disaster for being fortunate enough to have such a solid lead. Hence, now the game becomes figuring out whatever it takes to get the other player to put more chips in the center of the table. In the case of slow play, checking that monster is giving up very little value in exchange for the chance of inducing a bet. This is where knowing your oppoent can have a big effect on your net profit. Slow play the aggressive players and bet into the calling stations. Or just put in a fairly small bet for added value (also sets up profitable bluffs with small amounts.)

Of course if you know this and your opponent knows this and knows you know this... Great game, eh?