Willfully and gleefully helping to destroy people's lives. My brain normally just shuts down at such a level of awfulness, which means it's probably worth trying to understand, at least at the intellectual level. I mean, is this just straight up sadism? Is the guy just happy ruining stuff, a child knocking over blocks, except that he's in a grown man's body? Doesn't seem implausible, but I don't feel like I understan…
As somebody interested in peoples' motivations though, this seems puzzling. Outside of the modest burst of media attention he gets for doing it, I don't see a reason why he would add addresses to his site's pictures. The idea of mapping personally identifying information about people to certain unique numbers or addresses isn't a new concept as http://www.dirtyphonebook.com and other sites use numbers and things of that nature to link peoples' identities. But I think that inviting people to list an address is probably crossing one bridge too far.
Unfortunate.