Re: I don't see how this affects botnets.

This is not how botnets generally work.

Although some may use hardcoded IPs, the majority now keeps kind of regular expression of domain names (like bot*.net) and will more or less randomly try to resolve the names until they find one that works (like botnet1.net, botnet2.net, or botbot.net, etc.).

If the malware can resolve the name longer after it has been de-registered, we clearly have a problem.

Cheers