There's a reason our Communication Studies department is jokingly referred to as the Department of Facebook Studies.
  1. The Friendster testimonial.
    I don't know that there will ever be a social networking feature as great as the testimonial. There is no humble in this brag: I was really good at them. The idea that the core of Friendster was "My friends are so great, you should know them, too!" was and remains 💯.
  2. The Twitter retweet.
    Unlike the Tumblr reblog (which I find endlessly confusing*), the retweet is a painless way to spread information to others and ensure the original source is properly credited. Comedians get credit for their jokes, news outlets can claim continued relevance when they've earned it and, most importantly, the average person can impact, immediately, public perception of current events. *because I am An Old
  3. Collaborative playlists on Spotify.
    If you are not already doing this, here is my free tip for you: create a playlist called 2015 (or Today's Hot Jamz, or whatever). Invite your friends with good taste in music to collaborate on it with you. Whenever someone hears something new and exciting, just dump it in. It's a constant work in progress, but everything is coming pre-vetted by people you respect. Guaranteed to inspire some fun disagreements via text and make those end of the year lists much easier.
  4. The ListApp suggestion.
    Not even playin here--I really love this part of ListApp! Because almost no list is really ever finished, and collaborating is fun.
  5. The original Facebook status message.
    A controversial choice, I'd suspect, but I really liked the focus on the present tense of "Catherine Carrigan is..." I think it also placed an emphasis on activity and emotion, which are two of my favorite things.
  6. Flickr tags.
    Oh yeeeeeeahh, continuing to kick it old school with these choices. Before Instagram there was Flickr, and before Twitter put a # in front of them, there were just photo tags that you used to help other people find your photos in search. Which is how a picture of a sandwich I took on vacation ended up in a travel guide to Montreal (with proper photo credit).
  7. statistics.
    These days it's pretty impossible to keep track of everything I listen to on different devices/platforms, but I'm just enough of a music geek to have really, really loved stats. I particularly loved forgetting that I'd set them to auto tweet so once a week I'd be like, "Yeah, I *did* listen to that Jens Lekman song 14 times in a row the other day!"
  8. Likes/hearts/stars/+1s/[thisisgood's]/etc.
    On the one hand, it's hard to think of a more impactful feature on social networks. But they have a dark side. We've all had that feeling when something we thought was really witty didn't land or a photo didn't garner the praise we were, yeah, okay, totally seeking through inappropriate means. "Only three likes? Really?" These can feed the nasty impulse to curate our social media presence to present only the shiniest, happiest parts of ourselves. DISlike.
  9. MySpace Bulletins
    They were like the original news feed slash Tweet. So much potential.
    Suggested by @charlie
  10. Chatroom away messages
    Suggested by @vp