Back in 1986 the US wasn't as sue happy as it is now. Everything gets litigated now, it's the common sense thing people are talking about. Common sense died some time in 1997 and now we sue for everything.BUT,since Disney didn't respond in any way to the 1986 incident,I'm thinking they feel like they HAVE to respond this time in a big way.
The signs aren't to protect people they are so the company won't be liable when somebody does something stupid, much like warnings on lawn mowers and such, they aren't place on the mower to stop people from being stupid they are there to stop people from sueing when they are stupid.