Growing Closer On Facebook
In reference to this paper by Burke, et al.
Although it is indeed very possible that Burke and Kraut make a valid point, I personally do not believe that interaction through Facebook is the cause of these stronger relationships. Burke and Kraut claim that the strength of a tie between two people on Facebook increases as they have more one-on-one communication, such as personal messages, wall posts, and photos. While this may be true, I believe that the cause of the stronger relationship lies outside the social network.
Specifically, the reason that two persons may increase their frequency of personal messages and wall posts is simply that they have become friends outside the network. This outside cause could be for infinite reasons; for example, the pair of people may have recently become work colleagues or classmates. Because of this outside force, the two have become closer friends. Therefore, their communication through Facebook has increased, at which point the researchers notice an increase in the strength of the friendship. It is a textbook case of correlation vs causation.
To support this claim, consider someone who has recently met, for example, a friend of a friend. The two become friends on Facebook. It is highly unlikely that purely through Facebook, these two will continue communicating. It would, in the general case, require several more meetings in person in order for the two to get to know each other better, and therefore become better friends both on and off Facebook.