Survival of our species/Being careful with powerful technology
From AdCiv
This seems fairly obvious one. As technology continues to increase in capability and sophistication, the more damage an individual or small group is able to do, and more damaging the consequences are from an accident or oversight.
More complex technologies need more complex management. The great spectres of the 20th century were nuclear, biological and chemical weapons - all potential weapons of mass destruction. In the 21st century we be able to add genetics, nanotechnology and robotics - all technologies that could give us even finer controlled WMD.
How do we peacefully benefit from these technologies without increasing the chances of unstable individuals or fanatical groups using them against other people?