Thanks tembow, that does explain the address and the questions I raised in my previous post. You can ignore my previous post, which I was in the process of composing when you posted the answer.

That is a good point ;) Something to ponder too...

Any idea what the "situation" between China and Korea is? :)

Perhaps this...errr....may be what is intended....? err, no i didn't say it :P

I know when I originally started using Complainterator I think I questioned the use of that address too...

Being a fan of the "hosts file" I figured, why not just route to localhost/127.0.0.1?...Or even, nullroute it to 0.0.0.0 ;)

Perhaps it is a "limitation" of the registrar interface (whatever they use to lock/set/remove glue records, etc) so 61.61.61.61 is the "magic number" (for some anyways...hehe)

But yea, some blackholes (I think tembow covered most of them mentioned) are referenced at the spamwiki as well:
http://spamtrackers.eu/wiki/index.php?title=Black_hole

The reason for not requesting 0.0.0.0 or 127.0.0.1 or a 192. or 10. address is again based on experience.

Each registrar develops a "front-end" tool, or a "back-office" tool, that makes requestd from the registrar to the registry simpler.
Back in the days when I used to request such addresses, I received responses from some registrars that their registry system checked that the addresses being entered were valid, and did not allow those.

So my philosophy has been to ask all registrars to do something that is possible for everyone. It saves time and gets the results first time.

But thanks for your suggestions for improvements.