*runs to stock up on 9V batteries and steel wool for camping gear*
I'm kind of worried about their ending statement "only 9V batteries". Nope, my uncle got a AAA to light his pocket on fire once.
If you short any battery it's going to heat up, and maybe explode. Having the two polls on opposite ends makes it less likely, but it can still happen.
I like to store batteries in glass jars.
(Oh shazbot last week I threw four AA batteries in the center console in the car...)