Location: Somewhere in the middle of the Pacific Ocean
As I understand it, likely letters are sent out in waves from late January to early March. This is for students who Dartmouth want to help them "round out" the class. There maybe something about you that they like, could be academic, could be geographic, or it could be that the Admissions office thinks that you would be a great fit for Dartmouth. The likely letter sends a not-so subliminal positive message to the student early to attract the student to Dartmouth, because once the student is accepted at other schools the shoe will certainly be on the other foot. There will still be over 1500 acceptance letters going out, so hang in there everyone.
Yeah I couldn't believe it when I read it either---don't get me wrong I congratulate all that have gotten likely letters and some of the stats are amazing and the letters well deserved I am sure---I also get the recruited athlete set asides---but I have to be honest after seeing all the amazing stats for those rejected or deferred (my D is one--still hoping to get in RD and still loves Dartmouth)--this left a little bad taste in my mouth--again congrats to those who made it.