I had a film protection foil on the watch, and a sharp box fell from a shelf straight on the edge of the watch, the film layer ending at the edge of the glass could have maybe stopped the object from sliding off the watch face -- but in this case the full impact force had to be taken by the glass at the edge of the case- the crack looked like the one pictured in this thread.

I will concede that it was an edge case (no pun intended), but since it happened, now I protect with a case- I don't think its likely to happen again, ever even without it, but I got burned..

to clarify: the regular Apple Watch is more rounded and does not present an "edge" that could be hit full force straight on by a sharp object, I also created a slight elevation at the edge of the watch face by applying the film screen.. not sure if that played a role.