The August 2007 issue of Passagemaker has an article of an almost new Nordhavn 47 that was dropped about 2 ft. The aft strap broke while it was in the hoist having it's bottom cleaned. The boat
was a write off. Punched a fair portion of the aft bottom out.
The author says that dropping boats is more common than people realize. There was a quote, something like "small boats are dropped though carelessness, large boats are dropped because of equipment
failure". The article has ideas for contracts if you are going to have your boat
lifted and/or stored.
They also mentioned an incident where a boat fell over starting a chain reaction. One of the boats had just been refit
and was likely a write off. .