I recently had an event at a venue I had not been to before, and while advancing the show was told that there would be lots of good power. Upon arriving, I found a branch-circuit distro that at first glance had a couple red flags. I pulled out my tester and found that the branch circuit distro was wired with a 3 wire cord instead of 4 wires, which are required for safe operation. The person who assembled this had wired the three wires to the two hot wires and neutral, leaving the ground unconnected.
It was clear this device had been this way for a long time, and apparently no one had ever tested the power to see if it was safe - or if they did, they never informed the venue management. Thankfully the venue had other power I was able to use, and the show went on successfully.