Some people might consider flashaholism a mental illness, which would mean none of us would be able to fly...
Anyone else heard about the incident on Northwest Airlines yesterday? On a flight from Los Angeles to Honolulu, a male passenger began acting strangely, not listening to the flights attendants, wielding a phone cord like a weapon, and threatening to kill a baby that was nearby. Then about ten minutes prior to landing, he charged up the aisle towards the cockpit. There were NO air marshals on board, but several of the passengers tackled the guy, who was then restrained until landing. What is this world coming to???
Regarding banning the mentally ill, I don't think that's going to happen. Perhaps the most that can be done is for airport personnel to watch for unusual behavior, and determine whether someone can fly or not.
Ever watch the show "Airline" on A&E TV? It shows actual Southwest Airlines activity at several different airports--you get to see all kinds of people. I don't know if it applies to all airlines, but Southwest agents apparently have the authority to deny boarding to any passenger--usually because they appear drunk.