Anyone blocking mine and anybody else's exit from the plane in an evacuation would be getting a firm push onto the seats out of the way. Find it amazing that people value their laptop more than the lives of over a hundred people on board a plane
The simple solution to the problem of people messing about getting bags in an evacuation is get rid of the overhead lockers, job done. The ones that don't contain the cabin crew's emergency equipment that is. Also reduces the security queue.
To do this successfully though there would have to be major improvements in baggage handling as at the moment I wouldn't trust them to get a piece of bubble wrap to the destination unharmed. Anything I can't afford to lose goes in the cabin, that said though, without doubt it would be getting left behind if I heard the words evacuate!