Winter 2011/12 on a BOS - ORD flight ahead of a winter storm. GA and RCC agents announced that captain wanted to leave 20 min early and they would begin boarding immediately. We boarded very quickly with both the Capt and FO on the jetbridge and in the cabin helping things along. We pushed 30 min prior to departure and, based on the loads, my guess is we left some folks behind. It looks like BOS effectively shut down shortly after our departure.