Yeah there's a bunch of doomsday theories surrounding this, as there typically are.
No risk, no reward. The risks are pretty low, there are plenty of events that generate far more energy out there that we've observed. But until we try we really don't know.
Then again, maybe that's why we don't see any advanced civilizations out there.. they hit this stage, turn on their own LHC, and *blip* gone.
