I'll start with one from a friend of mine (who shall remain anonymous): he lives in a place with old 120V electrical wiring. He put a rig of ~1.6kW (~13A), as measured by a kill-a-watt, on a 20A circuit for about half a day, until he started smelling smoke in his apartment, apparently coming from the wiring inside the walls. He completely stopped using this circuit, and now runs his rig on a dedicated 240V circuit. A 20A circuit is normally rated 16A for continuous loads by the National Electric Code, but that old wiring was likely defective and the insulation probably started melting.