<p>You can only sign the guestbook once, so each entry = 1 person. I think it's possible that students who chose to defer matriculation for 1 or 2 years would still be allowed to sign the guestbook. I dont know the statistics about how many people actually do that, and you also have to remember that students who deferred matriculation from one or two years ago will be entering in this class, so I can't imagine the number would be affected by that very much. </p>
<p>They're either systematically going through the names and deleting people who declined the offer of admission, or the system does it automatically and all 1085 people who are on there right now will be bona fide MIT freshmen. Also considering its unlikely that EVERYBODY who accepted chose to sign the guestbook, that'd be a significant over enrollment. So if we're gonna use the guestbook and the guestbook alone, I can't see the waitlist being very useful this year. But it'd be silly to draw those kinds of conclusions without knowing the whole picture. Just be patient and wait for admissions to blog something.</p>