Today (May 30, 2018) I'm updating this page to let folks know that they should immediately cease using the Spam Cannibal blocking list.
The Spam Cannibal DNSBL has been around since at least 2003. It was started by a gentleman that I think prefers to be anonymous, so I'm choosing not to name him. It was basically spamtrap-driven, though I believe it would sometimes list /24 blocks of IP addresses in response to some spamtrap hits. It wasn't that widely used, but back in the old days, it often put the fear of god into marketing senders when seeing a hit against this list on their favorite DNSBL checking tool. This was also good in that it helped to drive marketer understanding of how sending to bad addresses can cause bad things to happen. As the list was primarily spamtrap-driven, it was mostly safe for hobbyist mail server use (in my opinion, anyway).
I reached out to the publisher of the Spam Cannibal DNSBL He let me know that the DNSBL is dead and gone. It is no longer an ongoing concern.
Fifteen years is a pretty good run, if you ask me. I wish him best of luck on any future projects.
May 31, 2018 update: The operator of Spam Cannibal is working with some smart folks to shut down the list in a graceful fashion. While there is no longer a "wildcard DNS" issue, the list is no longer being updated and is retired; you should still remove it from your mail server configuration.