"the chance of this happening is like you winning the major prize on the lottery 3 weeks in succession; the problem is that people believe it is possible to win the lottery 3 weeks in succession." -Frank Close
Creating black holes are not actually a problem. An black hole that could be created by a particle accelerator would vaporize almost instantly due to hawking radiation (yes there is stuff that "comes out" of black holes). The only real risks are stranglets that transform other matter into strangelets or singlarites that rip a hole in space time. This risks are also negligable since we have observed collisions of cosmic rays at much higher energy levels than can be produced on earth.