I saw this happen last year at the ramp...just now remembering it.
While I was waiting to use the ramp, the guy I was waiting for started driving to the top. Apparently he didn't know you need to strap the boat down.
About half way up the ramp, it flew off and hit the asphalt. He managed to get it winched back on the trailer, (with my help pushing it) the prop was smashed, outdrive broken, hull cracked. Looked like about a $10k boat...and he said he had barrowed it. 