Came from 64.94.163.146 and .147. Whois maps to:
Meaningful Machines INAP-NYM-MEANMACHINE-0652 (NET-64-94-163-128-1)
64.94.163.128 - 64.94.163.159
Never requested robots.txt
60k requests in an hour, about 17/sec.
Blocked it with setenvif:
[webmasterworld.com...]
(Yeah, they really were MEAN)