Originally Posted by Brian Diez
They aren't as heavy as wood, so if you land on the edge, like you're not supposed anyway, then it'll flip.
Still, no one gets a serious injury from missing a jump on a foam box.
I'm hesitant to switch to foam plyo boxes, especailly ones of unknown quality. I have a sneaking (completely untested however) suspicion that they may result in more achilles tears then standard hard surface boxes because the athletes heels sink lower into the edge of the box at the top, placing the achilles in loaded position at both jump and landing.
When I played basketball through high school and university we were always wary of courts thathad too much bounce or cushion as they resulted in more knee injuries. We all know a shoe with a heavily cushioned heel is bad news - i'm not convinced we should go all in on foam boxes until they have been around a while longer.