Its no news really to whoever is familiar with swatting, but this is something that recently came into the light in the public media as a few people have been found guilty of this real bad prank.
What is swatting? It's basically someone calling the 911 service, spoofing the callerid and pretending to be under attack from some maniac. What happens then is that a SWAT team is sent to the residence on which the spoofed phone number is registered. Obviously the end result is the SWAT team end up harassing the family / residents living there on behalf of the person who spoofed the call in the first place.
Quite a nasty joke if you ask me - and VoIP caller-id spoofing makes it very easy to pull off.