There are certain things that threaten civilization:
The bird flu (with the potential to kill hundreds of millions of people, this shouldn't be taken lightly).
Corporate hegemony, the idea that the government is essentially in the pockets of corporate interests, and place corporate interest ahead of the rights of the people.
Fundamentalism, the idea of rejecting human rights, due process, and tolerance in exchange for literal interpretations of religious texts.
Peak Oil, and the upcoming energy crisis. Civilization is currently powered by oil, and what if that runs out?