I mean, I disagree COMPLETELY with pretty much everything said in this post - David Fincher not an auteur (of course he is, all of his films have the same feel, look, atmosphere and touch that is distinctly his), unlikeable characters (a character doesn't have to be LIKABLE for us to empathize with them - is Michael Corleone a LIKABLE character? Is Jake LaMotta?), relevance of this movie to Facebook at ALL except for incidental relevance (Facebook is a McGuffin, it could have been ANYTHING else and the script would still have been just as good), Fincher's "disappointment" in the film (I still think this conclusion was taken out of context; sure, he was frustrated that Zodiac didn't get any attention, but I don't think he thinks any less of THIS film because of that), etc.
But, to each his own. If you didn't enjoy the film, there's nothing I can do to convince you otherwise, only hope that you'll give it another chance later on down the road and realize what a brilliant piece of narrative storytelling it is!