A week of ice storms and rolling blackouts (January, 1994).
That ignited an interest in prepping, though I wasn't conscious of a label for being prepared for emergencies.
September 11, 2001 moved my prepping interest up several notches (I live and work in Washington, D.C.).
My interest in wilderness survival (which is/was the ETS emphasis) began with an intensive series of hikes in the Blue Ridge mountains to help a friend get in shape for a Himalayan trek.
Back to prepping: the more I consider the various disaster threats (especially TEOTWAWKI scenarios like a massive EMP), the more I'm inclined to believe that our survival, as individuals and as a society, cannot be ensured by even the most well-equipped solo silo.
So I'm back to preparing for the most plausible - power outages brought on by storms, earthquakes and occasional local or regional power grid failures.
Being in DC, terrorism is a concern but does not seem so imminent as it did in the first couple years after 9/11 and the anthrax attacks on the Senate.