For a non-athlete, training to failure might bring with it the need to manage recovery, but since performance is not necessarily an issue, its less of a problem. I have not heard of any reports of increased injury or health problems that are out of the ordinary, but I haven’t really looked at it that close.
The other aspect of this is for those who do associate great workouts with complete exhaustion eventually (at least from what I’ve witnessed in a few cases) begin to fall off the wagon. I’ve found they are so beaten down from chronic, long-term fatigue and actually grow to hate the training because they don’t believe it can be both sub-maximal and effective. I think Cross-fit promotes this mind-set.
I guess the proof is in the pudding. If what you say goes for Crossfit, then it will boom then fade away. But from the OP’s comments, it seems as if crossfitters are everywhere.
I’m not so sure that the cross-fitters have any better injury rate than the average recreational basketball, hockey or tennis player. The people I’ve spoken with who are “reformed” cross-fitters stayed injured. Granted that’s the experience of only a few.
I don’t know for sure either, but weightlifting and other resistance exercises, even if to failure, have lower injury rates than most other sports.