While I'm never that person that mass delivers business cards to everyone in the room, I believe that these parties can be the best networking opportunities. However, since alcohol tends to run freely at these things, one would have to put in the extra effort to be remembered. I learned the nuances of drink just so I could network better at these things. Not too little, not too much. I want to appear to be a fun person, not a social outcast or pariah. Just a little of the courage juice goes a long way.
Striking up conversations with strangers poses some difficulty, but it can be achieved. I'm a foodie, so usually I connect with strangers by discussing the food at the party. Seriously, who doesn't love food? One could argue Americans tend to love food too much!
Networking is a two-way street, however. I have, on many occasions, encountered people who are just not interested in connecting. I never take this personal, although I honestly have wondered why one would choose not to socialize at a party. Their loss. I've had my shy moments, too, but usually after a 15-30 minute "warm up," I'm ready to socialize. I guess some people never get over that fear.
Happy Holidays and Happy Filmmaking!