As someone who would be likely to get a yellow card at any tournament where that system is used, I've got to say, if I was handed one and nobody else around me was getting them, I'd be pretty bloody embarrassed. I think that factor is high enough for most reasonable people that they're not going to go out of their way to exploit it....and I say that as someone that is very...VERY..bad at containing their emotions.
I about blew out someone's eardrum next to me when I finished Jericho at our local location a few weeks ago. Was only the third time I've managed to do it, so I was understandably exited and the location is loud....my volume was WAY WAY over what I intended, heh. I expect that if I did that at a big tourney, I'd probably get some kind of warning..maybe not a yellow card but definitely a "please don't do that."
But hey, on the upside, Iron Man is gone now, BUT I got to finish Jericho one last time.