A new version of this report is located at ProPublica. Includes more detail and a comment from Susan Prosser, Vice President of Industry Relations at DomainTools, about the how the DomainTools "IP Explorer" tool gathers the "C block owner" value.
The new version mostly just adds information, but previous versions of this gist can still be seen at the "Revisions" button to the left. Earlier versions should be considered draft quality.
An earier version of this gist had the wrong IP address (220.127.116.11) and the gist has been updated. 18.104.22.168 was reported by @Baneki, and was widely disseminated on Twitter, but the original reverse-engineer dump by @vlad902 had actually reported the address as 22.214.171.124.
126.96.36.199 and 188.8.131.52 are both part of the same "unknown" IP address block that is not allocated any more specifically than UUNET/Verizon Business, and the WHOIS for both respond with the same data. None of the conclusions below have been affected.