Eliezer, the cosmic ray argument *doesn't work* against black holes or strangelets; cosmic ray collision products have a large momentum relative to Earth whereas some of the particle accelerator collision products would end up going slowly enough to cause damage. There are, however, other strong arguments against both the black hole and strangelet scenarios, for which see http://lhc2008.web.cern.ch/LHC2008/documents/LSAG.pdf (note that the author confirms the part about the cosmic ray argument not working). In the black hole case, for there to be a disaster, it would have to be true that 1) LHC unexpectedly creates micro black holes, 2) Hawking radiation unexpectedly doesn't work, 3) it eats the Earth with unexpected speed, 4) especially given that micro black holes don't seem to have eaten neutron stars.