Pass makes an interesting point...this is true for live play...you can make the wrong decision based on reads from another player if the other player doesn't know what he is doing.
This happened to me this past weekend:
$1/$2 at Harrah's New Orleans. Stack sizes are $700ish each. Player is a loose passive black guy that calls anything pre-flop.
I am dealt K

6

UTG +1. I raise to $10. He calls on the button. All others fold.
Flop: 9

6

2

. I lead for $13. He calls. Turn J

. I check he bets $10. I call. River 2

. I check. He bets $25. I took a little while as I really thought he was bluffing (this type of player makes small bluffs and huge value bets). I call and he says "I was just bluffing...I only had a 9" which he did and I lost. Point is: I knew he was bluffing because he thought he was bluffing. It's a weird dynamic - right call right reasons bad result. He did come from the $4/$8 limit game and that games plays way different than even 1/2 nlhe.
As a side note, Will Ferrell and Jason Sudeikis sat down and played for about an hour at the table next to me at about 1:30. Nice guys fun to be around.