You'd think they'd know if they have a black hole or not. But apparently it's only speculation. BBC : Lab fireball 'may be black hole'. Or you can read the rather mathy paper, The RHIC fireball as a dual black hole.
I'm presuming it's not going to eat the earth up because in tiny fractions of a second it doesn't get big enough to be stable and thus flies appart when they turn off the juice.
Anyway, while we wait for the earth to collapse, there's a highly amusing Slashdot discussion of the alleged phenomenon.