I used one for a couple of years with no problems. I always made sure the potatoes was scrubbed and wet(I think thats the key) and the bag was always clean. Until... I baked a sweet potatoe one night and the next night did a white potatoe without washing the bag. It started smoldering. I think it was caused by the juice from the sweet potato.
Warm Tater has no scrim(glue) to melt or catch fire but any cotton fiber will burn. I did look mine over afterwards and the burned part was strictly on the inside surface where the juice had leaked out. The bag itself and batting had smoldered but did not burst into flames. So I caught it early when I smelled smoke. Anytime I used one, I always stayed right there, just in case. I still use one and like it. I think the potato is fluffier. But I will never walk away and leave it unattended.