Kishnobi why do u disagree with that rule if there is noone else to act?
the only reason i can think of is if someone on the table (not in the hand) makes a comment or something...
There are a number of reasons I think it"s wrong.
One, is the reason you stated. You turn your cards over and someone comments that you"ve lost one of the cards you"re drawing to as they held a particular card, or that if they"d called they"d hit the whatever.
It"s also the same as declaring your hand. You"re trying to get a read off the player (and other players who are no longer in the hand). A player might even do it to get the other player to reveal his hand before the showdown - and therefore making his hand dead as you"re still to act. It"s angle-shooting.
I saw a televised event, not sure which one, and Gus Hansen showed his cards to a player sitting next to him in exactly this situation. the TD stepped in and said his cards were dead. I thought this was fair.