Here's the explanation I received from the HD when they found the Food Saver in my kitchen. Even with the best sanitation practices, it's possible to have botulism present. Botulism is an anaerobic organism, meaning that it thrives in a vacuum. It creates a toxin that is heat stable, so proper re-heating does not get rid of that toxin and that's what makes you sick. One of the functions of a commercial sealer is that it raises the temperature of the wrapper to 185* (I think) to kill any of the bugs that are on the plastic wrap.
Brian Sweeney - CBJ #3691 - '77 Step Van Mobile Kitchen, Horizon Marshall, WSM with Pro Q Stacker, Weber Kettle & Smokey Joe GOLD.
"Any sufficiently advanced technology is indistinguishable from magic" - Clarke's Third Law