Why is this so? Why is it that Google monetizes so well on Search while having a hard time on social properties?

researchers found evidence that the brain reacts differently to people who seem like us. How can this inform design?

As good design further penetrates the Web, once highly-regarded conventions fall into disfavor and are replaced by more effective ones. Yet some flawed conventions persist. In fact, they persist on some pretty high-profile websites; to their detriment.