I found Ellis Hamburger’s view on what’s wrong with Facebook quite interesting. From Facebook’s friend problem:

In the real world, losing touch with people happens naturally and effortlessly, but on Facebook, unfriending is reserved only for breakups and acts of malice. So, the ghosts floating through my News Feed vastly outnumber the friends I’ve kept. My Friends list went from a roster of my current friends to a collection of everyone I’ve met in the last 10 years — a social group too massive to feel urgent, and too broad to share with on a daily basis.

Facebook is broken for its earliest users, and perhaps soon, for many of its new ones as well.