What I've observed leads me to believe most individual efforts are motivated by fear. Middle-class folks with some resources to spare will get their bug-out bags ready, realize how long it's been since their CPR certification expired, and replenish their emergency water cache when they're afraid. No surprise Katrina's made some people (even well outside of the disaster swath) very uneasy.

As for volunteer groups, I don't know what motivates people to organize and/or join their local CERT. I wish it were politically popular to support such a thing, because that sure would make it easy. Guess we have to work without such an easy solution.