Seriously, car companies turn out new cars every year, but it seems that no one has run a cost-benefit analysis on car alarms since they were introduced.
1. A disturbingly high number of false alarms. Seriously, any other product with this many false positives should be pulled.
2. The duration of the alarms. Why is it that about 25% of car alarms fail to turn off until someone actually jacks the car and tears out the speaker wires in desperation?
3. The intensity of the alarms. Why must they be so loud?
4. Chain reactions. This comes from #3, where one alarm is loud enough to set off another alarm. Actually, this could get rather humorous.
5. The sanity of the surrounding peoples. 'Nuff said.
Benefits: If you happen to live in a remote area with no neighbors for miles around and the alarm goes off, you might have a few seconds extra to reach for your shotgun.
Then again, I might just use the shotgun on the cars anyway.