9/11 and the Oklahoma bombings are pinpricks compared to the damage that could be wrought by a nuclear weapon.
"Unhappy parties" (Love, the term by the way, been to a few of those in my time

) want nuclear weapons. They've wanted them for a while. We already know that. One day they will get hold of one. One advantage of the Cold War was the real threat of nuclear holocaust ensured people kept a much more careful eye on nuclear weapons and material.
Now we have a collapsed USSR, with nuclear weapons scattered across half a dozen countries of variable repute, we have states of questionable intent such as North Korea and Iran potentially developing nuclear weapons, we have countries in highly unstable situations with nuclear weapons (think Israel) we have nations that are increasing hotbeds of Radical Islam with nuclear weapons (Pakistan) and who knows what else is happening on the nuclear front that we are unaware of?
It's a matter of time. It will happen.
-Gumboot