I'm feeling this now. I was watching a Soccer game from the sidelines (read, I'm on the field) and a Soccer ball came right at me and hit my arm wearing my Apple Watch 4. I thought nothing of it as it didn't hit me very hard. After the game, I looked at my watch and saw a round shattering of the screen glass with about 4-5 hairline cracks coming out of it and going all the way across the screen.
I was shocked at the amount of damage, and looked into getting it repaired. I think it's like $300 to replace the screen since I don't have AC. Actually, from reading this thread it sounds like Apple Care would not have covered it anyway.
Wow, just wow.