Tiger's 15th hole - chronology of events as I understand it:
1 - Tiger hits flag and ball rolls back into water.
2 - Tiger places ball 2 yards further back from original lie.
3 - TV viewer calls in to alert rules committee of possible infraction.
4 - Rules committee says "no infraction".
5 - After the round, Tiger interviewed on TV and says He intentional placed the ball 2 yards further back to avoid an identical shot hitting the flag again. Makes sense to me, but he is creating an advantage for himself. That's not cricket.
6 - Here is where I get confused ... Rules committee re-evaluates, and says yes there was an infraction (2 stroke penalty), but we can't Disqualify him because we initially ruled there was no infraction. Either that, or there is a new rule that says you can't disqualify a man for making an honest mistake.
The rub here is that Tiger sought to gain a 2 yard advantage, but I believe he also thought he was allowed to do that since he was gaining yardage.