Tempered glass shatters into small pieces so there won't be as much gore if someone does fall through a piece.
Yup -- we once owned a 1987 Chevy Astro van. It was sitting in the driveway and the window in the sliding door just exploded into tiny pieces. I thought maybe it got hit by a BB, but the glass guy told me he's seen it before -- the glass might be under stress and it just decides to let go.
