Questions about the validity of previously calculated blackhole creation probabilities at LHC are discussed in this New Scientist article.
The conclusion? We don’t have a clue of what the range of probabilities are. It is however still small compared to, say, getting hit by a car or dying in a plane crash. Questions about the validity of calculations are legitimate. However, I am not sure if I will enjoy thinking about the implications of this particular question (especially if it leads to more wailing from those who are scared of blackholes). How do you arrive at a decision weighing probabilities on something like this. Is it fine to risk our existence for more knowledge when the risk is once every billion years, or is it fine if the risk is quantified as once every trillion years? If we decide it’s too risky, are we going to wait for another billion years to run the LHC?
If we go, I say let’s go with a bang. The fear of unknown is such a spoilsport. Let us be reckless with the LHC and really push it, taunt Nature to show us what it has got. Give us Higgs or give us a Balckhole, dammit.