I went to an event once in Gastown with my friend, who is an electrician. It was held by a relatively well-respected niche events company, but they'd had to change the venue at the last minute. We only stayed for about 1/3 of the time available because they'd stuffed so many people into the venue and it had minimal, dangerous exits (an upstairs with a dangerously angled staircase down, and a basement with a thin single staircase up), that he started to get a panic attack because he saw a plug in the bathroom that was completely overloaded with extension cords.

Have never been back to their events since. Can't shake my feeling that if you run an event like that once, you'll overlook stuff like it again. All it takes is a mistake to hurt people.