Really, the IP trail is a pretty solid tracking mechanism. As an extension of that, DNS logging helps as a more visual-friendly fingerprint. I imagine a lot of players don't travel much, so a dynamic IP should at least be recognizable from their closest hub point. I know I play from my home and a friend's place, we both have Comcast, and I know the DNS puts me out from St. Clairsville, OH (even though that's not where I live, but you get the idea) from either location.
The only real monkey wrench in this with my past administrative experiences has been when dealing with AOL. They don't seem to break stuff down into regions with their DNS, instead just assigning whatever random IP they have free from their leased sets of octets. Understandable given the sheer size of their user base, at least back in the day, but a nightmare when you were trying to stomp a problem AOL user because to block them, you had to block all of AOL. In these particular cases, you'd almost have to deal with AOL more directly to determine whether or not the log-in point was outside the norm.
I'm honestly boggled that things have gotten this far with character loss and the extreme delay of restorations. I would've thought it common sense protocol by what I've learned over the years as just a basic net jockey. Though, I guess it's an example of plausible deniablity in that it's technically not SE's fault the accounts were lost. Still, it wreaks of shoddy customer service.
____________________________
Violence good. Sexy bad. Yay America.