"spiral of silence"

"mean world syndrome"

The Salem Witch Trials are the best-known example of mass hysteria. The McMartin Pre-School case and the Tulip Bulb hysteria are others. The dotcom bubble probably qualifies.

Scott, you're forgetting the elevation of the Holocaust to the level of a new religion. Or maybe you're still PC enough that you don't dare mention the sacred Holocaust.

Mass hysteria bubbles are something like Rover in The Prisoner, they swallow up the incautious in order to bring them back into the group.