Unless I'm missing something, this is a pretty avoidable bug, and really only puts you under the stage on very thin stages like Smashville, Town and City, and some Omegas. Other stages you just clip in to the stages and can jump right out. The timing is strict enough so you have to be devoting to this to go for it (no way you're getting people on blind reaction). If you know about the glitch and don't suck, you're not likely to be caught into it, and even less likely to die seeing as you're probably going to be on a stage where it doesn't kill you.
This is no worse than wobbling or Brawl grab infinites. It's always been part of Smash's ruleset to know the characters, and it's your fault for losing a game due to a bug, even in insane situations like Sheik Chain jacket game crashes. It's even weaker than the previously mentioned insta-kill bugs because your opponent basically has to walk into it on purpose to die from it, and even then that's only on like 2 stages. There are no (known) set-ups for this, and it doesn't even kill outside of thin stages, nor is it difficult on any level to avoid. In some situations, it's actually WORSE to do this glitch than to just leave your trampoline up, as on stages thick enough where someone can jump back through the bottom, they can potentially punish you since you're in special fall after initiating your Up-B. The only times bad bugs have been banned are when they result in indefinite stalling like Ice Climber's freeze glitch and MK's IDC, and this in no way stalls out the game.
It's a stupid bug, and hopefully it gets patched before EVO. I can see how at a glance people want to start thinking up rules to avoid this, but it's a pretty irrelevant bug. I'd be incredibly surprised if someone landed a kill with this in bracket (anything can happen in pools...), so saying that this glitch, let alone Pac-Man, would need to be banned at EVO if this isn't patched out is incredibly uneducated and over-reactive. It's probably not even worth anyone's time to think about this bug, as a insta-kill glitch that your opponent basically has to cooperate with in order to perform really isn't going to effect the game.