Yes, there should be a penalty. If you have a dry side pot then at least one player is allin and at least two are still active. If you happened to be colluding with the allin player you might want to push the active players out of the hand with a bluff. Unfortunately there's no way for the other players to tell if you're just a hopeless donk or are actually colluding. Don't do it. Also, you must bet/raise on the river with the nuts; Chris Moneymaker learned this and it cost him like a half hour of play. Same reason: soft play is not allowed in real tournaments.