yeah I don't think there's actually a problem with volunteers, it's managing the volunteers whilst you have search and rescue operations underway.  
You can't stop people from helping, or sending supplies etc. 

Also, if the more untrained civilians are doing things in dangerous places where there is still active risk, then it become a problem. People need to understand this as well. Cleaning some mud isn't the same as rushing to a place to go see what you can do only to get in the way of trained professionals trying to save lives. It happens a lot.