The builders of the world's biggest particle collider (LHC) are being sued in federal court over fears that the experiment might create
globe-gobbling black holes or never-before-seen strains of matter that would destroy the planet.
Article can be found
here
Some doom sayers are scared of such notions as:
Runaway black holes
Strangelets
Magnetic Monopolies
I actually feel sorry for the lawyers on this case.