A nice bit of Facebook horror appeared on the Reddit NoSleep board. It has the appropriately long title of "My dead girlfriend keeps messaging me on Facebook. I’ve got the screenshots. I don’t know what to do."
The story poses itself as a cry for help from a young man increasingly scared of Facebook content seemingly coming from his dead girlfriend. Formally, it's a sequence of paragraphs arranged in chronological order, each linked to a screen capture of some creepy bit of Facebook activity. The narrator sets up each graphic, then reacts to it.
For example, here is one of the early exchanges. "Nathan" is the story's narrator, the boyfriend; "Emily" is the supposedly dead girlfriend:
Note the anonymizing features, which add a documentary feel to the story. And note, too, the final open text box, which gives an extra sense of ongoing conversation.
Later the exchanges become more like a ghost story. For example, this screenshot shows Emily complaining about temperatures - of the grace, most likely: