Check out this terrifying New York Times article.
"Walter L. Wagner and Luis Sancho contend that scientists at the European Center for Nuclear Research, or CERN, have played down the chances that the collider could produce, among other horrors, a tiny black hole, which, they say, could eat the Earth. Or it could spit out something called a “strangelet” that would convert our planet to a shrunken dense dead lump of something called “strange matter.”
Lisa Randall, a Harvard physicist whose work helped fuel the speculation about black holes at the collider, pointed out in a paper last year that black holes would probably not be produced at the collider after all, although other effects of so-called quantum gravity might appear.
As part of the safety assessment report, Dr. Mangano and Steve Giddings of the University of California, Santa Barbara, have been working intensely for the last few months on a paper exploring all the possibilities of these fearsome black holes. They think there are no problems but are reluctant to talk about their findings until they have been peer reviewed, Dr. Mangano said."