Maybe it works by a registry of current and former students and faculty at Hogwarts, and people who are neither show up as "Intruder (number)" or something. In modern Wizarding Britain this would include basically everyone.
I mean, if the Founders created the Map as part of the Hogwarts security system, they wouldn't have been all that concerned with putting a name on everyone who could possibly step foot on the grounds, they'd just want to be able to locate students and differentiate them from anyone else.
I can't remember, did the Beauxbatons and Durmstrang delegations show up on the Map in GoF? Not that it really matters, the canon!Map and MoR!Map are different enough that it wouldn't be much evidence.
This theory, unlike the birth certificate one, can easily explain how the Map matches people with names. During the Sorting, McGonagall reads aloud a name, and the next person who puts on the Sorting Hat is assigned that name. (Assuming the Hat is hooked up to the security system, or vice versa.)
The new thread, discussion 13, is here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With three chapters recently the previous thread has very quickly reached 1000 comments. The latest chapter as of 25th March 2012 is Ch 80.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine, ten, eleven.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: