I might be old fashioned, but concept of user statuses that are visible to ~all their contacts. For people who don't meet each other IRL all that often this is a way to notice that the other is involved in something that you'd want to talk about.
#LDJam: Decided to submit to Extra instead of Jam so we can be more relaxed while developing the game, both because my brain has turned off today, and because another member of our team isn’t feeling too well.