"This is a decision that millions of social media users make sometimes several times a day; in a world where a Facebook friend request costs nothing more than a single click, the 'friend economy' faces an overabundance of friend inflation," he writes. "Given that reciprocal friending -- that is, friending someone simply because he or she friended you -- is often the norm, users sometimes find that their friend feeds and follower lists become so cluttered that they're virtually unusable."