Added bonus, nitrogen gas is super cheap.
As far as ways to die go, you could do much worse. The only group of people who would be distressed by it would probably be fighter pilots since they're trained to recognize and work around low oxygen situations.
In other words, no, it never really works. That level of violence is self-defeating. ISIS is finding that much out themselves though, because all their Muslim neighbors (and *especially* Jordan) hate them with a passion. I agree that the U.S. needs to help put a stop to them, but cancers like ISIS do tend to get killed off pretty handily by the rest of the world.
the NSA can use coffee cups to playback conversations from half an hour ago because of reverberating echoes still trapped inside the cup.
(I just made that up, CSI writing team: give me attribution please.)
On last week's episode of CSI Las Vegas they had a no-audio web cam quality recording of two guys chatting in a green house and they used (I shit you not) vibrations from the leaves to rebuild an audio of what the two were saying. I face-palmed so hard.