Peggy Orenstein writes in the New York Times about her use of Twitter. Here is part of her commentary which references famous sociologist Erving Goffman:

Back in the 1950s, the sociologist Erving Goffman famously argued that all of life is performance: we act out a role in every interaction, adapting it based on the nature of the relationship or context at hand. Twitter has extended that metaphor to include aspects of our experience that used to be considered off-set: eating pizza in bed, reading a book in the tub, thinking a thought anywhere, flossing. Effectively, it makes the greasepaint permanent, blurring the lines not only between public and private but also between the authentic and contrived self. If all the world was once a stage, it has now become a reality TV show: we mere players are not just aware of the camera; we mug for it.

According to Goffman, every social interaction is actually like a theater drama as the individual actors look to play a role that ultimately saves them face. The advantage of Twitter, and other social software, is that it always a user to craft their performance at their own convenience. A user can reveal what they wish, when they wish.

Goffman was also interested in the divide between this performance and when an individual could be their true self. Individuals travel between these front-stage and back-stage worlds. Some users might feel they are revealing their true self in software like Twitter but I think this is unlikely. The act of tweeting or operating in front of a camera includes the knowledge that someone else is going to see what is revealed and this inevitably changes the action. Perhaps we can only truly be back-stage when we are in situations where they will be no human interaction. Goffman was also interested in these situations, such as when we are alone.