One-time Yahoo administrator Derek Balling has announced that the RFC Ignorant blacklist is being shut down. This blacklist has existed since at least late 2001. Its listing criteria including things like not having an "abuse" or "postmaster"address that accepted mail. Listing criteria didn't necessarily overlap with the generally accepted criteria for fighting spam, so my guess is that this blacklist's lack of usefulness as a spam fighting tool had finally diminished past the point of no useful return. As Derek himself says, "the usefulness of a DNSBL is greatly diminished," and of the old hardware running the service, "the value proposition just isn't there."
I blogged about the RFC Ignorant blacklist back in 2006.