cantSUPenough said..
I wear one in the bigger waves and when there is a strong off-shore wind - on numerous occasions I have had the board get caught in the wind, go straight up, and come straight back at me. I was once surfing and it happened to another guy. He cut his head and hurt his neck.
One problem, I tend to be a little braver with a helmet on...
Like Cantsupenough said I wear a Gath on bigger days and strong wind condition. I had the exact scenario happen to me but I was out cold and was rescued by a mysterious surfer who to this day I have no idea who he was. I suffered concussion and amnesia and spent a day in hospital. Never did get memory of the incident back but I bought a helmet the next day