the chris mass holiday could make for a quiet week. but one company gettings to oech its prent early on why tomorrow is so big for the facebook. this coming wook brings some big changes for one particular social media giant. facebook will start trading on the s&p 500. it could be part of your retirement portfolio sometime soon. and, of course, that does mean more money for facebook. also, wall street will celebrate christmas this week. on christmas eve, trading will end at 3:00 p.m. it s also the final week of the year, a time we usually see what s called a santa clautz ral