I heard about something like this many, many, years ago, but I don't think it's very common. Any electric appliance can catch on fire, and ones that produce heat (toasters, coffee pots, slow cookers) are especially prone. Manufacturers these days have safeguards built in to most of their products and, of course, the instructions always tell you to regularly inspect for any damage, frayed areas, etc. And NEVER use pins to hold it in place. That is a sure fire way to cause a short circuit.

A much more common problem with heating pads is getting burned because you fall asleep and/or do not have a good sensation of how hot it is getting. The one I bought a short time ago has a timer to shut it off after a pre-determined amount of time. I don't think I will ever use another heating pad without this feature.

Mike