Amid Mexico's escalating drug violence, grenades have become the latest weapon of choice used by drug gangs, with many of the grenades of Cold War vintage and manufactured in the U.S. or Eastern Europe, according to a recent Washington Post story. So on hearing that a grenade which wounded at least 15 people was detonated in a nightspot in Puerto Vallarta, a destination once popular with tourists from the U.S. and elsewhere before the surging violence, it was easy enough to assume that someone had rolled a grenade into the bar as part of the cycle of attacks and revenge....