I don't believe I've ever worked at a company that had mandatory holiday parties, and I've seen a variety of holiday parties in my career. One company had big, formal affairs where they rented a ballroom in a fancy hotel and you were supposed to dress up and come; I think the only cost to the employee was a cash bar if you wanted drinks beyond the issued drink tickets. I never went to those.
The parties here are during the day and they close the office from 3:00 on; however, this year it looks like they're changing that and planting it in the middle of the day. Not sure if they're closing the office or not, but it implies that they aren't. I generally go because I get free beer and some snacks but I generally grab them and go back to my desk to nef. :awe: