I liked how he totally loved his own joke about having invented poking ("I invented poking! :-D"), and after a second of silence from the audience, realized that he should be in character, and went back to trying to look serious.
To be fair, it was a pretty good line. One thing I like about comedians like Jerry Seinfeld and Larry David is that they both realize when they've said something hilarious and can't help but giggle a bit. It works for Zuckerburg too, although I guess the audience didn't care that much.
I thought that bit about poking came off pretty awkward. As did the rest of his appearance. That doesn't really matter though, he is very successful outside comedy and public appearances.
