As this topic has appeared in Aircrew Notices, I thought I might point out that this week's New Scientist has highlighted an interesting approach to this problem.
Quote: GOOD to see that Virgin Atlantic is taking a tough line on aircraft vandalism. On a flight from London to San Francisco recently, the flight attendant waited until the plane had reached cruising altitude before announcing over the PA system:
"This is a non-smoking flight. The toilets are all fitted with smoke alarms. It is a criminal offence to tamper with them. Anyone caught tampering with the toilet smoke alarms will be forced to leave the flight immediately."
http://www.newscientist.co.uk/feedback/