10 times a game winnie. You probably see it so often you don't even know you are seeing it.
Do me a favour, if you can drop the homerism long enough to do it; next time you watch a game, any game, count the number of times when that someone gets hit into the boards with enough velocity that if it were a metal post instead of board, major damage might be done.
10. times. a. game. Easy.
Now, wander over to NHL network or Classic Canada and watch a full game from the 60's or 70s. Hell, even better...watch a playoff game, where the intensity is ramped up. Hell...watch that roving band of idiots called the Philadelphia Flyers.
You won't see it. You won't. I sat down a couple of weeks ago and watched game 2 of the Stanley Cup finals from 1974, and anytime anyone got near the boards with the puck, they were angled out, or manhandled with a glove to the face...but nothing like what is ok today.
Granted, it was also ok to empty out the benches and punch someone until they were a bloody pulp, however I digress.
There has been 25 years of gradual erosion of the rules until we have arrived at this point. Was the hit unacceptable? Yes, by the rulebook definition and the way it was called up until the mid 80's. Was it uncommon? Only in the sense of the 1 in 100000 luck of what and where he hit and the damage done.
Blame the game. This day was coming for a long time, and it has arrived.