Sounds like more of a fire hazard than an explosive hazard.
A hearing hazard indoors, anyway, if one is not expecting it. I think there were recalls years ago with one brand. Static sensitive. That said, the person would probably be OK, because they ARE like little firecrackers..But I suspect it's a quick way to lose interest in reloading, should it happen. The problem is when they are in the primer feeder dish on a progressive press. The operator may end up wearing little pieces of plastic from the primer feeder cover, but everyone wears safety glasses when they load, right?
But not when they toss a package on the ground...