This is a terrible idea for many, many reasons. I'll list them.
1. No one cares about facebook anymore. This movie would have made a lot more if they made it in 2007, when facebook was at its prime. Now everyone is just sick of it. Stupid applications, privacy violations, annoying layout changes. The novelty has worn off and frankly, no one cares to even use it, let alone learn about it. I would liken this to making a movie about the guy who invented the buggy whip, to steal from Other People's Money.
2. It's cookie cutter pretentious. I'm glad someone else mentioned how annoying the trailer is. It follows the same trailer every other movie does.
(Show someone with an idea or facing a problem.)
(Show how much of a FUCKING GENIUS THEY ARE HOLY SHIT.)
(Show people having sex with a darkened gradient, because everyone has sex in shadows.)
(Show things going bad.)
(Make a joke.)
(Title.)
Christ, haven't we had enough spray tanned college strippers from the transformer series and Nickelodeon? Speaking of, what's London Tipton doing in college?
3. The acting is going to completely suck. I'm not blaming this one on the actors. Far from it. But there are just so many more interesting things in this world than talking about a website no one cares about. If I told YOU to talk about youtube for an hour and a half could you POSSIBLY keep up enthusiasm? No.
4. The last time Fincher did a non-metaphorical film was Alien 3. Enough fucking said on that one. What was he thinking? He found his true talent (and I used to hate the guy until I saw his real movies, with metaphor and good premise). I just don't get what he gets out of it. What are you supposed to learn about yourself watching that douchebag Zuckerberg?
5. Everyone that worked on facebook has sold out. You know that fact is going to be nagging on a lot of people.
6. There's no zombies and that's just pathetic.
7. 90% of movies are in college these days. GROW UP ALREADY.
8. They're going to make Zuckerberg and Facebook look like Jesus Christ. There's going to be no mentioning of the controversies like the private information trafficking, the unnecessary updates and layout changes, the addition of features that remove privacy, the stalking, the hackjob applications, and the aforementioned selling out. It's going to be some bullshit heroic tall tale.