The best short summation of it I have seen is David Denby's.
The debate about the movie's accuracy has already begun, but Fincher and Sorkin, selecting from known facts and then freely interpreting them, have created a work of art. Accuracy is now a secondary issue.That was published October 4 (in The New Yorker, and online only by password). Since then, a great deal more has been put forth to show how the film's version is in contrast to documented events. But Denby is right. It's a movie, and it ain't a documentary.
If it says something true about people, it's okay that it isn't particularly true about the people who build Facebook.
The difference is that the events depicted in this movie are so recent, so public, and so widely documented that it's easy to compare the movie version to documented events."Everyone" knows the film ain't exactly as it happened, and everyone seems okay with that. It's a kinda sophisticated take, I think.
With historical fictions about more remote events, that kind of sophistication doesn't get engaged so much. Crude debates about "how true is it?" take over, and historians are expected to take the "not very" side. But Denby's rule applies. If they are any good in themselves, "accuracy is a secondary issue" in historical fictions. If you want to argue about accuracy, write history. If it's fiction, the issue is if it's any good.