This is the kind of thing that worries me about geocaching. Remember the lamp-post cache (LPC)?
Suspicious container forces evacuations at Anaheim Plaza | anaheim, martinez, container - News - The Orange County Register
ANAHEIM – A report of a suspicious container left in a light pole led to the evacuation of three businesses, but a bomb squad determined the package was part of a game, police said.The small, pill-bottle type of container held a note that said "something to the effect of 'congratulations, you found it,'" and appeared to be part of a game of geocaching, a type of "high-tech treasure hunt" in which people hide prizes for others to track down using GPS devices, said Sgt. Rick Martinez of the Anaheim police.