I'd say improper use of extension cords would be #1 and fuse tampering would be #2. I get so mad when they report a fire on TV news and cite the cause as being electrical. Later they report that three portable heaters were plugged into a 100' 16/3 extension cord. That isn't an electrical fire.....That is a stupidity fire.
Something tells me that aluminum wiring is going to get thrown under the bus on this report too.
