MOUNT LAUREL, N.J. (AP) -- Superstorm Sandy has brought out generosity far and wide in the biggest U.S. relief effort for the American Red Cross and other groups since Hurricane Katrina swamped the Gulf Coast in 2005.

And while the response is heartwarming, some of that is also helping create a "second disaster after the disaster," in the words of one expert.

It's a common quandary after natural disasters displace lots of people and destroy homes and possessions. Relief groups need very specific things, along with cash and organization. Instead, they get vases and vacuum cleaners, or interference from well-intentioned volunteers who think they're helping but are just hindering efforts.