I actually have to agree, with both sides (though I lean heavilly toward the barbs side).
First, players should be keen to make sure that their items aren't waiting to get stolen. Be cautious.
Second, It is not only the DM's game. By saying the DM can do what ever he wants, it takes loads of fun out of the game. True, he should take the advantage when he has it, but blatantly attacking a PC without any reason other than "you are using the item in an inovative way that disrupts the way that I (more bit****g and complaining)" If a DM sees an unbalanced item, he should make sure that their is a plot hook so that the item is taken temporarily. And, by the time the character gets it back, it won't be unbalanced anymore.
A DM who says 10 harpies fly out of the woods and steal your junk to one thirteenth level char, might as well say Azmodeus says give me your soul or die, to a group of 1st level chars. Either way its not fair.