I was at a conference on this type of topic. It was geared towards IT students and the presenter made everyone sign a waiver coming in and told everyone not to use their computer in that room. (Smartphones weren’t super popular yet)

Anyone who jacked into the ethernet ports had their Facebook and Skype “hacked” and the presenter changed their picture to himself.

It was a wonderful experience seeing all the chaos that ensued. That kind of automated mitm attack won’t work like that these days but maybe something to that tune.

Edit: plus it’s a good lesson to read and comprehend what you’re signing.