I don't know if they ever blacklisted them all, but a boatload
of them were showing malware a couple months back.

Paul

Yes, they have been blacklisted.

Read through

free third-level domain regisrty blocked by accident - help "legalize" cz.cc - Webmaster Central Help

There are many people complaining about banning of .cz.cc domain. Google use to ban such domains when it finds malicious content over the domain.
I guess, this is not completely right way to tell people to scan their domains... because all accounts on this domains are suffering due to shady activities of few people...

.ce.ms , and .cu.cc will be banned soon I think.. because millions of that subdomains used for spamming and 90% sites of these are trash .