The security of the even isn't in question. It's the security of the phone.

If you have your phone in your pocket in a locked Faraday cage, it prevents compulsive checking and any network notifications. It also means coat-check folks don't have access to it. The fact it can record other attendees doesn't matter. They may have their phone just in their pocket.

Typing that out, it makes me realize the Faraday cage is unnecessary. Just turn it off, lock it in a reinforced sleeve, people at the front hold onto the key for you.

Surprised I didn't realize this immediately. I sometimes lock my phone in a bag and put the key in another room. If I'm really serious I put the key in an envelope and write on the outside why I'm doing this. Tearing the envelope makes a nice barrier.

Had to do this recently at a show for a headliner comedian.

I did expose a flaw in their system though: they only bagged one phone (I have a second one for work).

It’s not a system that holds up to an adversary. It’s at most a semi-voluntary restriction.

But this fails if someone forgets the second phone.

I don’t think they meant security as in taking it into a secure location, they meant security of your own data and software on the phone by not leaving it where strangers could have physical access for hours.