Laughing, no, I don't mind. It sucks when someone makes a joke of some kind and there's this dead silence and then people are like "That was funny dude, I loled." Actually laughing is much more genuine.
Granted, you shouldn't hold down your vent key for an entire long laugh, that can get annoying, but I actually prefer it when I or a guildie shows that we're actually chuckling or laughing at something funny.
Sure, if someone has a consistently obnoxious laugh, and always feels the need to keep their mic open for 30 seconds while they're cackling away, that's overkill. But I don't think that you CAN'T for some reason, laugh in Vent. Just don't be a dumbass. And, of course, coughing and burping an shit is another story.
EDIT: Also, your poll comes off as pretty biased, it's sort of funny. :|