I know 2 people who are here only because of a last-minute "OK, I'll wear the helmet" decision: me, and a guy I used to work with.
He only put it on leaving work that day after a couple of us busted his stones, and on his ride home he needed it.
In both cases, the bikes were totaled, and the full-face hats were sacrificed.
If you could predict the future, you'd be a Lotto winner, right ?