Part of the problem is just plain oversensitivity (alarms being set off by passing trucks and such), and part of it is bad design. For example, my alarm will go off if you close the trunk. That's completely nonsensical: when the car is secure, the truck will already be closed, and opening it would be the appropriate trigger. But it does mean that I occasionally set it off in my garage because I left the trunk open, locked the car, then came back and closed it.