You should never do anything at a poker table if you can't give a well reasoned reason for doing it. In my opinion at an online table it's virtually impossible to peg your opponents level of thinking, so it's virtually impossible to know how your show will affect all of your various opponenets. Also, if you're multi-tabling it's nearly impossible to keep a mental rolodex of player levels, if you can peg them, and how you've used them all. Sometimes in a live game if I'm feeling like I'm in everyone's head well enough I'll use a show to manipulate image, but it's important to remember that if you have thinking opponents who are giving you credit for being a thinking opponent then you might not have the desired effect, which could be very very bad if you assume that you've outfoxed people and blow off a stack on a
bluff, or overbet and make them fold because they didn't just think you were a donk like you'd hoped. All the thought that goes in makes me inclined to say just don't show, at least not if you can't give a well reasoned reason for doing it to say more than half of the opponents at the table. And remember who you don't know what effect your move has had, and watch, and maybe learn what effect, which will give you information on how they are playing beyond just that. Hope all that was clear, game theory has a nifty way of convoluting things.