Not a silly question at all, Peep-Chicken! I can understand your concern. But I have a towel, Press 'n Seal, and straw packed under it, on top of it, and around it, and it's just fine. Same with the others who have switched to this method. None of us would be doing this if we felt we were jeopardizing our homes, families, coops and birds. Far, far less fire danger than with a heat lamp. Think about this - the heating pad heats the cave and the chicks. A heat lamp heats the bedding, the brooder box, the dust and dander, the surrounding floors and walls, and you certainly wouldn't let your hand or a piece of paper come into direct contact with it like you can with heating pad.
Of course, any heat producing device - or for that matter any electrical device - carries with it some risk. But heating pads are designed to come into direct contact with human skin, clothing, bedding, and upholstery. For that and so many other reasons the pad is less risky than the lamp.