"Facebook, for example, encourages phatic communication through sociable add-ons like 'vampire bites', 'zombies', 'hot potatoes' and automating messages encouraging participation between friends in quizzes, film taste reviews and the like.[6] Furthermore, Facebook's new 'beacon' technology creates an environment where one's online purchases and interests get relayed to one's network of friends through automated communication. Twitter encourages phatic communication through the imposed limits of the medium itself. The 160 character limit for messages creates brevity in communication. The lack of a private messaging facility, promotes generic 'announcements' over dialogue or targeted conversation. "
(Vincent Miller, 2008, p.398)
[6] For example, a typical automated message such as ''Mr X' has challenged you to a movie quiz' suggests a personal invitation to compete. However, it is usually the case that if 'Mr X' has participated in a movie quiz, you will, by default, be automatically 'challenged' to the quiz, by virtue of being friends with 'Mr X'.
Miller, V. (2008). "New Media, Networking and Phatic Culture." Convergence: The International Journal of Research into New Media Technologies 14(4): 387–400.