To me it's a mob rule situation. If the vast majority of the crowd is standing up, or the people in front of you are, it's time to stand up. If you're the only one in your section standing up, I might get a little annoyed with you if I was sitting behind you.
That said, you gotta go with what you feel. If you've got ants in your pants and you need to dance who's to stop you from cutting loose! (just don't blame the dude behind you if you're bugging him).
The mob rule is why the Garden isn't as rocking as it should be. There are too many idiots at games who just don't know what's going on. The people around me last night stood and danced at timeouts, but when the game was tight, they sat firmly in their seats chatting or texting. Should I have followed their lead and only stood at the most inane time? Everyone at the Garden is a slave to the Jumbotron.
Not sure what games you have been attending. As a season ticketholder, I can tell you that the Garden has been extremely loud through most of the playoffs. Still has not reached the level of the 2002 comeback against Jersey, but it has been close a couple of times. As for standing up, I agree with the mob rules.
I do agree with Pawtucket though on the people who stand up and dance during the timeouts, etc. and pay little or not attention to that game. Unfortunately, that is why fans like us, who are at the games, have to put up with all of the crap that goes on at timeouts. Drives me crazy. Just play the games.