Some of the posters here have an interesting idea of the definition of negligence.
As far as I recall Negligence is any act or omission that a reasonable person might regard as likely to cause loss or injury.
If you do not insist on people wearing vests do they have a greater than 1 in 2 chance of being injured? The danger must be greater than I thought.
While I am certainly not against wearing a vest, and I do carry one in the aircraft I am very much against the suggestion that wearing one makes you "safe" and not wearing one makes you "unsafe".
Mike