Although The Social Network is many things, I can't help but see it first and foremost as a movie about a friendship falling apart. It's probably for personal reasons more than anything, but the relationship between Mark Zuckerberg and Eduardo Saverin is so beautifully written and believably performed that when their bond begins to slowly unravel, it's devastating. There's an exchange early on, when Mark is still in the early stages of development and Eduardo notices that his name is featured as co-founder on the Facebook masthead, that really caught me off-guard this time around:

Eduardo: "You have no idea what that's gonna mean to my father."
Mark: "Sure I do."

Eisenberg delivers that "Sure I do" in such a casual, off-handed manner that you immediately get a sense of how well Mark and Eduardo know each other; thinking about that, in comparison to where the two characters end up, is enough to make even the hardest heart break.