I have been going to conventions since sometime in the '80s -- Creation Star Trek cons, NorWesCon, GeoCon, FaerieCon (more recently renamed FaerieWorlds), OtaKon, Sakura-Con, Star Wars Celebration, Dragon Con, SDCC, ECCC... I have never seen metal detectors, been searched, had my bag searched, or anything like that. Some I have been to have "weapons" checks to make sure prop weapons are fake or inoperable, to varying degrees of consistency or competency. And even then things that are part of a costume can often cause more damage, like spikes or wings.
Just as how the TSA has intercepted zero terrorists since 2001, this kind of security theater does nothing but comfort the easily comforted and annoy just about everyone else. The determined crazies find ways around, as they always have, and everyone who was not interested in causing anyone harm are the ones who pay the price. I have several real weapons for various costumes because there are no replicas for those obscure ones and I would have to get them anyway to make such, even if I had the setup to do so, which I don't. I know how, and, more importantly, when to use them. I wish I could go through an interview and sign something attesting by both parties I know what I'm doing and won't recklessly brandish, threaten, or harm. But, since I'm the only one who knows I won't use them, I leave them home so no one freaks out. It irks me.
I remember ren faires where people knew better than to whip out live steel and be idiots with it. I remember motorized squirt guns that were highly accurate, properly colored replicas of the real deals and people didn't panic. I remember being able to walk people to or meet them at the airport gate. It's such an irritating miasma now of some people being stupid, other people being irrationally fearful, still others not having their psychiatric issues caught and treated at a young age.. And we intelligent, responsible people who just want to responsibly have fun... can't.
--Jonah