The discussion came up last weekend about whether or not players should fold when there is no bet to them. My take on it is that it is a legal move but bad etiquette since it can affect the play of the hand. And when the game involves showing cards such as in Stud games or Pass the Trash then the potential effects of open folding are even more pronounced. As an example, let's assume that Player A has a Ten high mixed suit low. Everyone else at the table has paint showing except for Player B showing a Trey. The player who has the Ten high would almost certainly fold to a bet if he had to act before the Player B but if Player B open folds his hand before Player A acts then Player A knows he can for sure lock up the low and will seriously affect the play of the hand. Additionally, every card that the open folder turns over is potentially critical information since those cards cannot show up in other player's hands.
In PtT I don't feel that any significant information is given away by flipping cards over in a hand that one doesn't plan on playing. And I'd say that any modicum of information that is given away is far outweighed by the importance of protecting other players in the hand.
There is much discussion about the matter in this 2+2 thread.