Similarly, observers have been puzzled or concerned by seemingly irrational behavior on SNSs. Users may spend considerable time updating their pages, adding new pictures and music; the comments they send each other are often in the form of jokes and images. Why spend so much time on seemingly inconsequential changes of imagery and uninformative communication? Deep concerns have also been raised about young people who create overly revealing profile pages, in which they appear in provocative photographs or recount illegal activities such as drug use or underage drinking. Warnings about the dangers of doing so have stopped some, but not all. Why would someone choose to post such material once he or she was aware of the negative consequences? Signaling theory can help explain such behavioral phenomena.

While an outsider might see as wasted the time expended on profile updates and exchanges of the latest pictures and URLs, another interpretation is that these seemingly trivial activities are examples of online fashion, signals of social position in an information based society (Donath, in press; McCracken, 1998; Thornton, 1996).

Fashions, the constant change in the way of doing something, are signals whose form—the currently popular object or saying—changes frequently, while the meaning—social position—remains the same. There are fashions in clothing, slang, and management techniques. Their individual instantiations are easily-copied conventional signals; it is the constant evolution of forms that creates the reliable signal. Fashion is about information, about knowing the changing social meaning of an object or way of doing things.