Repeated Blacklisting / IP reputation

THAT would probably be easy enough to detect; RIR simply checks to see
if new DNSBL entries had appeared, and refuses to trade in the block if
any do.

You may need a few more refinements too.

I don't think it's technically unworkable, if tackled correctly. But it
also leaves some questions, such as what ARIN is expected to do with the
toxic wastelands left behind by spammers.

... JG