Is a snapped chain a more common occurrence nowadays with the advent of 11 speed blocks and narrower chains? I still ride my 1980s bike with its 6 speed block and Sedis(?) chain. I'd never heard of anyone snapping a chain unless they hadn't refitted a rivet correctly. I was mystified by a report of a bad accident that I'd had 2 years ago and posted on the web; it quoted " A cyclist was riding along the Formby Bypass this morning when the chain on his bike snapped.The chain got caught up in the bike wheel sending the rider over the handle bars smashing his head on the kerb.". I have no memory of the accident and when I picked the bike up from the police station several weeks later the chain and the rest of the bike was OK. If the chain had broken, I doubt it would have ended up in the front wheel causing me to go over the bars.
No, 11-speed chains will not break easier than say 6-speed chains. The converse is true. With an 11-speed (or 10-speed for that matter) system you have stronger chains because the sideplate holes where the rivets go through are countersunk and the rivet is sunk inside that so that it is flush with the plate. They do this to make the chain narrower. The sideplates have not gone thinner, it is just the space proud of the plates that have shrunk. This countersinking actually makes the chain stronger against breaking open from bending sideways. Note that a chain never "snaps" in the sense that it breaks in tension. It always breaks from bending sideways.
Below 10 speeds, the chains are actually weaker in the bending mode. This is a) because of the rivets which are not countersunk and b) because of the narrower space between sprockets. The narrower the space between the sprockets, the less the chain straddles two sprockets during a change and thus the less chance of it receiving a forceful side pull during a poor shift. Further, non-hyperglide chains have rivets that are only partially peened, usually on two sides. If you look at those pins you'll notice the two opposing cords on the circle. If you look at a hyperglide chain's pin head on, you'll notice that it is peened right around. This looks like a circle on a circle, and is much, much more difficult to pop than other pins.
That description of your (?) accident is completely inaccurate and was made up by the reporter. A chain doesn't snap, it doesn't get caught in the wheel when broken and the reason for the bike coming to a sudden stop (and you keep on travelling) had nothing to do with the chain getting caught in the rear wheel, let alone the front wheel.
