bacteria forming in reheating of baked potatoes
Because potatoes are grown in the soil, they are a natural source of Clostridium botulinum. C. botulinum could grow in a cooked, foil wrapped baked potato that is not maintained at proper temperature because the combination of cooking and foil wrap create an anaerobic condition. C. botulinum requires an anaerobic (oxygen-free) environment in which to grow.
Bottom line: wash your potatoes, don't use foil, cool properly, reheat properly and you'll be fine.