Two, one by suicide and another who succumbed to a disease.
One. My wife’s cousin died from an epileptic seizure in December, aged 27. She was due to get married this spring. 
Actually, her fiance closed down the page a while back, so she no longer shows up in my friends list.
Weirdly, my Yahoo mail still shows a conversation tab at the top for a friend of mine who died in an accident 5 years ago. Even when I closed it down it was there again next time I logged in. I just leave it now.
Just one, but his account has never been memorialized. People still write on his wall all the time, two and a half years later.
One, a co-worker who died young of cancer this year. Her husband maintains it and posts now and then, and her kids and friends still post to her wall and tag her in pictures and posts.
One. A classmate who died of cancer two years ago.
One. A in-person friend (what is the terminology for someone you regularly interact with outside of Facebook anyway?) who was killed on his scooter by a drunk driver a couple of years ago.
I don’t know if his actual page is up, but there’s a “Memory of” type page or something similar for him that’s still up.
One- my former husband, who passed away in July.
Two. My 100-year-old great uncle (not that surprising), and a colleague that I sang with in 2009 who had sinus surgery and died of complications (about a month after we met). She was 33. Her last post was complaining about the swelling and it being difficult to breathe. People still post regularly to her timeline.
Two. One is my Aunt who passed away last summer and is maintained by my cousins, the other is a college friend who commited suicide and whose family chaned his page to a memorial page.
One. My mom died last June and her facebook page still shows up. We had our differences but I sometimes want to cry when I realize I’ve put up pictures of her granddaughters and she won’t see them.
Just one, Autolycus.
None, but I don’t have over about 20 friends. With two exceptions they are all at least 28 years younger than me.
Four. [expletive deleted] cancer.
None dead, but one guy turned into a homeless case. It kind of freaks me out when my feed shows one of his “likes”, as I know he is sleeping under a bridge somewhere.
Dead, one (co-author of my first book, who died about two years ago.)
Brain-dead? The vast majority.
Two. My father, who died over a year ago, and jan howard finder, who died this week.
Two, a cousin who died in a car wreck and a former colleague who died of recurrent breast cancer.
None (touch wood), but a dead guy I never met occasionally ‘invites’ me to events.
I regularly hang round with a lot of his old friends, one of whom is presumably maintaining it which is why I get the invites. It does creep me out a little, especially because there’s no hint at all that he’s dead anywhere on his facebook page, or his linked homepage, and he died around 5 years ago.
So two who succumbed to a disease.
None that I know of - but the ratio of ‘inactive’ facebook users to active facebook users among my friends is pretty high - I have ~140 friends but it seems like it’s the same 15-20 who update a lot. It wouldn’t surprise me to learn that someone who hasn’t been on facebook in a while is actually dead.