If one is to assume that friendships are, at least in part, utilitarian in nature, and that each party gets what they need or want from the other, it makes sense to assume that one's on-line connections are also serving some sort of inter-psychic need. While most people certainly use social media in order to get information, stay in touch with friends and for professional networking, it seems to reason that we are also using our on-line selves in order to attain peer validation, support, as well as project the exact version of ourselves that we want to be at the moment.
Take the profile picture for example--is it not exactly the visual that we would like for others to associate with the idea of who we are? Is it not a highly-produced version of our idealized selves, or at the very least, some version of the person that we would like to be? And as we continually update our profile pictures and updates, are we not asking our network whether or not they "like" us, thereby seeking the approval from those who typically have limited real-time knowledge of our "real" lives, and are not necessarily in the best position to provide that validation? It certainly appears that by happily sharing our lives on-line we are also choosing to put some version of ourselves in front of a large number of people who we may or may not really know, in order to see whether or not they like us. Or, more accurately, if they like who we are trying to be.
Perhaps not wanting to put oneself in the position of being judged by others has something to do with why some folks are so staunchly opposed to social networking. Or it may have something to do with simply wanting to avoid the myriad of feelings, ranging from joy and sympathy to jealously, competition, and even contempt that being privy to the accomplishments and failures of the "produced" lives of one's friends and acquaintances may engender.