Products by people like Arbor Networks (http://www.arbornetworks.com/ http://www.arbornetworks.com/) helps with this -- I think they essentially observe traffic

Products by people like Arbor Networks (http://www.arbornetworks.com/ http://www.arbornetworks.com/) helps with this -- I think they essentially observe traffic patterns and siphon what they detect to be DDoS traffic to alternate routers at the edge of the network to study and blackhole.