antiquark, everything you said is quite correct, but all of that does not help on case to case basis (or what i'm meaning to say, yes it is true, and it's quite logical, cause that's how the waiting list actually works, but it doesn't help us to guess will they go to waitlist for the class of 2012)
"I had never even *heard* of Facebook before I came to Caltech, and plenty of Techers I know still don't have a Facebook profile. Even if you ignore that plenty of people who have Facebook profiles don't join Facebook groups, it's a little silly to assume that nearly all admitted prefrosh will have joined the group, or that everyone who is still in the group is going to Caltech (or was admitted in the first place.)"
ok, but you came to caltech what, last year, two years ago, three (i'm not sure how long does facebook exist even)? but as facebook "grows older", more and more people are joining it, it became a necessity (i mean, half of my school is on facebook, and we're in a country in the middle of nowhere, with only 10% of population if not less with internet.)..
next thing, if you're excited that you got into caltech, and even more if you're sure to go, ofc you're gonna join the group! that way you can meet a lot of people, and talk about things, and everything... caltech dosn't have a blog thingie like MIT, there is no communication to anyone inside caltech in anyway except by the facebook.
Next, it doesn't matter if all of the accepted students have joined the group, but everyone who is still in the group is probably going to caltech because I've been watching the group for the whole last week, and from 250 members it went down to 210. reasons why 40 people left right before or around the 1st may?... because it's the decisions day, and they decided to go somewhere else.. it couldn't be a coincidence.
and in the end, yes, ok, i know that all of this is like shooting in the dark, but as you said we should relax... well this makes me relaxed heheheh
)) it makes me feel like we have some insight into what's going on.. i mean, if there were 250 members still in the group, i would start worrying, because that would probably mean there is 220+ students who will enroll (+ because of the people who don't have FB, and 220 because 30 members of the group are already at caltech) this way i know it's a 180+ number and it makes me feel a little better :P