[btown]

Looking at how it does reverse DNS lookups to try and map backwards... is there such thing as a crowdsourced database that resolves the most common domain name(s) that resulted in a given IP address? Seems like this would be tremendously useful for any sort of network tooling, but I can’t find any references from a quick search.

[nimrody]

You do realize that multiple domains may be hiding behind the same IP address? This is very common with CDNs (although the bigger players can afford a static CDN IP, I guess)

[creeble]

Robtex.com and some similar animals have some historic mappings, though of course not comprehensive.