I have had string break before but can say that I've ever seen a string snap, whip through the grommet and out if the racket and hit something. Especially poly. Just a freak accident I don't think it would happen again but you never know.
Everyone has the right to be stupid... it's just that some people abuse the privilege...
Balance - 31.0 cm, Weight - 358 g, SW - 346 Kgcm^2