The FBI swooped into a house in Rockwall, Texas when it emerged a gamer and physicist enthusiast was trying to create a small nuclear reaction in his house using Uranium.
It just goes to show how the internet helps to spread information – the man learnt how to make the mini nuclear reactor using online resources and then the FBI learned he was doing it via his online blog posts about his house doubling in radioactivity.
EDIT: In a similar ‘normal guy gives governments a scare’ vein, it looks like the recent confrontation between US patrol boats and Iranian Revolutionary Guard in the Straits of Hormuz may in fact have been a hoax by a local radio ham who regularly pranks passing ships.