Please just throw fish at me if this has already been proposed, but I was thinking today about what aspects of spamming a spammer finds hard to change.
Changing names and IP addresses are easy, but I imagine that finding a DNS server that will be authoratitive for them is a tougher challenge.
So, if one was to develop a list of the name servers that are authoratative for spam domains, then when a spammer changes but keeps the same name server, we will know and squash them!
IIRC SA 3.x's URIBL_SBL already works this way by checking authoritative nameservers for URLs.
