The Dead on Facebook

With over 900 million users on facebook I, as a digital archivist, wonder about the dead on facebook. What happens to their account? I'd guess no one calls up facebook to let them know a person is dead. 
So......how many users are dead? We already know that many of the accounts are fake or that people have multiple accounts. But who keeps track of the dead? Also.....I do wonder what happens to all those posts and the dreaded timeline. Does the company keep all of that info? 
I would argue they should. If the web posts we make today are the record others will look at tomorrow then we should keep this information public and preserve it for future generations.