Caller ID follies and SWAT teams, hacking PBX

There was a case of a guy tricking a 911 system to believe he calls from another place, and then social-engineering the police to send a SWAT unit to the premises.
http://www.pcworld.com/article/138591/couple_swarmed_by_swat_team_after_911_hack.html

A lot of possibilities along these lines opens when we take in account the often poor security (e.g. default or weak passwords) in today's low-cost PBX systems.

Another trick with hacking PBX is in issuing calls from them to paid lines and cashing in potentially fairly fat profits.