"Thrice Upon A Time"
James P. Hogan wrote a great story called "Thrice Upon A Time", in which a particle collider created black holes... The protagonists had to change the past at great personal sacrifice to prevent the collider from going online (This was long before Hogan became a total Velikovsky lunatic)
I am only saying that we need good proof that no harm will come from our actions before we do certain experiments.
So far I think the peer review process will do a fairly good job of preventing disaster.