Many years ago, I had just gotten home from inflating my off-the-bike tires at a gas station. I was getting the bike ready to install the wheels when one of the tires exploded through the sidewall. A few minutes sooner and it would have gone off in my VW Beetle. The sudden air pressure change would have ruptured my ear drums. Remember those air tight, floating Beetle ads? I had to roll the window down to close the doors with that car.
I think the so-so quality tire had a minor defect that took a couple of years to fail. OK, my regularly pushing those tires to their cornering limits may also have had something to do with it.
These days, ozone and UV attacking the rubber isn't helping any.