Adam Shostack 
When someone [you're talking to] asks you “what’s new” at a conference, the very worst answer is “same old thing.” You have a chance to remind them of who you are, what makes you special, tell a funny story like “I don’t think I’ve seen you since X happened...” Even if you want to say “same old thing,” you can say, ‘It’s amazing, but I’ve been farming cabbage for 16 years now! Whodda thunk?"
The reason non-answers are bad is because the conversational baton was just handed to you, and you're batting it away, rather than taking it. You're making the other person do all the conversational work.
Do you really have nothing you want to talk about? Why are you even at the conference?
Jonathan Yu@adamshostack I think it's unfair to expect me to be in a mood to socialize just because I'm at a conference. People attend for all kinds of different reasons.
Though I also agree, if you're trying to meet people, then it makes sense to be sociable!
@jawnsy I mean, I'm assuming here that someone wants to talk - they're at a networking event, or has come up to say "good to see you" or whatnot.
If you're not in a mood to socialize, it's totally fair to say, "I have to run, sorry" or even "sorry, feeling overwhelmed, not wanting to talk."
@adamshostack I think what I'm proposing is that conferences are not necessarily networking events for everyone at all times. I often go to events just to eavesdrop on others and watch a few random talks to keep a pulse on things. Same for meetups. I'm not always in a mood to be sociable :)