I would SERIOUSLY be disturbed to find out that this is something that's available out there. I don't do anything illegal, immoral, or - um. Well, fattening is something else entirely.... but anyway, I do NOT appreciate people wanting to circumvent what little privacy I still have.... and yes, I DO give complete information when I register a domain. That's beside the point.
It's just no one's business what sites I own. If you've got a law-enforcement situation, LET THEM DEAL WITH IT - if they will. Of course, they may not. "You pays yo' money, an' you takes yo' chances...."
[Keep FIRMLY in mind that we in the US seem to have a totally different attitude toward privacy than do people in some other parts of the world....]
Thereore if someone wants to hide he is able to do it fast and easy.
Ih other hands nobody offers service to find domain of THAT GUY. But several people have huge parts of whois database (e.g. Godaddy used to have no pictire-code protection)