Classic, "grab the bags" before evac thinking. I am just guessing, but I would put the percent of passengers who would get the evac behavior close to optimal is less than 10% on any given commercial flight in the US. Having been involved in some non-aircraft evac situations as a provider and analyst, that is the percentage I would assign in those too. I think its irrationally optimistic to think that any majority of US citizens in any crisis situation would make optimal decisions. BTW it was part of my job so I am not shooting from the hip.