you might have interviewed after they sent out 2nd round acceptances... according to last year they usually send out once a month at the very beginning. so this year they might have sent out the 1st or 3rd for people that interviewed in december and maybe they will send out acceptances feb 5th or 7th for those who interviewed in january... i dont know for certain but thats my guess
EDIT: check that. they said today at the interview... they meet once a month and give notifications at the end of the month.