its an iffy situation i think, i played my first live tournament a few months ago and i saw it happen, i didn't say anything but i thought in my head "how can they think that's okay?". i don't think its bad etiquette to ask, i think the bad etiquette was shown when someone shows a hand to just one other player.
then again, the thought that goes through my head is,...if there showing a hand at all, they probably dont fully understand the reason why most pros choose not to reveal there hands, even though they ALL know they can be seen on tv a few weeks later. so i think to the players that do this arent aware of the way it can make an avid player feel, or they just dont care because there too friendly with the other players at the table... if thats the case id say its okay, because if there "friendly" asking shouldnt be such a big deal, and if they dont know any better cause there ameture players, well i see no harm in that, if someone just told them the rule on it that should be the end of it.
im a firm believer in show-one show all, and other rules that were are in place for the fairness of the game, its very hard to have an edge in poker, i dont think one player should have an edge as big as seeing how a particular hand was played cause his friend is sitting next to him and wants to show his "uber-fold" or his "favorite" 27os hand that he check-folded after a bet pre.. thats the kind of info everyone wants to know, NEEDS to know to make good decisions against a particular player.
my final verdict... ask away.... let the whole table know your asking... they cant hide the hand then. lol