People forget to switch on Alarm Edit
Many intruder stories reported in the papers , we are not informed as to one key reason there was a break in: the occupants didn't switch on the alarm system because they were either to drunk of forgot. An alarm system should therefore activate automatically after a certain time. A person prone to intoxication must use an electronic alchol detector , that if not blown into automatically arms the alarm system.
Use an alarm system with Ethernet port from http://scratchpad.wikia.com/wiki/CompHomeAutomation to automatically detect that all occupants are inside after a certain time, automatically arming the system.