The problem is that if the router is configured to announce these IP's there is an instant flood of incoming traffic. You could set the edge routers to drop an

The problem is that if the router is configured to announce these IP's there is an instant flood of incoming traffic. You could set the edge routers to drop any traffic to 1.1.1.1, but that still means that the upstream bandwidth is consumed by accepting the packets and then discarding them internally. With routing at this scale EVERYTHING has a cost, you cannot just accept a blob of traffic without interfering with some other service(s). Every packet has to come down the wire, and then be handled by the router (either dropped or forwarded on). This scenario is basically an unintended DoS attack.