A couple years ago I got called to help out audio for a small community theater gig. The gear was set up before my arrival, but during strike I noticed the amps were plugged in to adapters just like that, with female edison to 1/4 inch adapters at the speakers. The "speaker cables" were whatever length of orange and green extension cord happened to be available Their "logic" was that using edison instead of proper cables meant that they could get longer speaker runs by going to a local hardware store instead of having to order stuff on-line. I made a bit of a fuss with their TD about the possible dangers of blowing stuff up or getting someone hurt, got a smile and a nod, and haven't been called back since.