Spectre once bubbled...
there was a big argument; I'm not sure if it was techdiver, the wahoo yahoogroup or somewhere else; but it had to do with the "bus driver" concept that some of the EDBA were commenting on.
I always felt that was the right attitude; not for the captains to have; but for the divers to expect. In my opinion it's your ultimate responsibility, and yours alone, to determine if your ready for any dive. It's not the boat captains, your buddies, your instructors, or anyone else to tell you "No". For a captain to provide anything other than bus driving services to and from a wreck is a _service_ they provide, not a litigatable responsibility. If they don't have O2 on the boat and you need it [for example]; that's not their fault; you should have brought it yourself.