ok, to get back to the original question... i'd say people are still holding multiple acceptances when they're not sure where they want to go yet. look at my signature - i'm holding both still cuz i don't know which i want to go to, and to be honest, if i don't get in anywhere else i'm gonna hold them both till may probably to try and get more information before deciding. now, if i get in somewhere i'd prefer over either of these schools i'll gladly drop them so other people can be happy about an acceptance. likewise, if i get in somewhere i wouldn't go over my state schools i'll decline that immedeately.
so i don't think most people are being selfish pigs, holding 5 acceptances, 3 of which they have no plans of even considering. this is a big decision, and a lot of us are just waiting to get more information (ie, financial aid info).