This topic is surprisingly gaining more attention for a culture typically described as 'death-denying.' But I guess you can't really deny death after it happens. It is very real then and probably easier to talk about since you may still have this online connection to the person even though in real life they are gone. I suppose it can be eerie to look at someone's last post that may have happened moments before they died like Dr. Frank Ryan who drove a car off a cliff moments after a posting to Twitter. 
Compiling all the information about us online through different social media platforms, it really tells a story about a person. A story full of life which reinforces what it means to be alive; pictures of friends and relatives, trips and celebrations, back and forth commentary with colleagues; all of this adds up to show a little bit (or a lot in some cases) about who we are.
And it doesn't have to just be the main social media platforms. There are hundreds of thousands of online communities that are losing parts of their group every day. A very moving online memorial I found on one of my favorite sites (Board Game Geek) from a husband about his recently deceased wife, Roberta Lukes. They shared a love of board games and he wrote a 'Geek List' of games that they had played together that helped weave the story.
Look at the number of supportive comments from people who knew him and his wife and from complete strangers. These acts of support and kindness in online communities are very interesting to observe.
So the next time you are talking to someone with a life threatening illness, ask them about their online life. While it won't get you any points towards a higher complexity of billing in the social history it may clue you into what matters to this person.