As some animals mature, they outgrow and shed off their skin, their exoskeleton, or some other part of their body. A replacement awaits beneath that might be larger, of a substantially different form, or simply fresh and undamaged. This process, called molting, is undergone by a wide variety of animals. This dragonfly, photographed by Böhringer Friedrich, provides an especially striking example:

We humans also molt as we mature, but it is our social identity, rather than a specific body part, that we outgrow. As we transition from childhood into our teenage years and through adulthood our preferences around the foods we like, the clothes we wear, the skills we practice, and the company we keep can all change dramatically. These changes are often relatively abrupt, like the physiological changes of many other species. Afterward we still enjoy reminiscing about what we used to do and we appreciate how our present self grew out of our past preferences, both privately and with others who knew us then. I fondly recall the Lego castles and spaceships that filled my childhood, and while I now build with other things and only really talk about those memories with my family, Lego still contributed significantly to my present identity.

The creators of social web services have yet to take human molting behaviors into account when designing their digital spaces. As a result, the changes I am able to make to my online profiles are either destructive or cumulative. On Facebook I can untag myself from old photos but then have no ability to go back and reminisce either alone or with the others who were there then. Alternatively, I can let the photos accumulate over the years, but then my entire social history is accessible to new acquaintances, and it makes me uncomfortable to have so much information available so soon in new relationships.

Facebook and other services do offer some tools for managing this problem. I can organize my friends into “Lists” and make different pieces of content available to different groups of friends, but I do not know of many people actually doing this in practice. It would be mentally exhausting to consider each of hundreds of people I know on Facebook and sort them into categories based on the time and place of our friendship.

People have, in contrast, shown a high degree of tolerance for friend request emails on new web services − I’ve both sent and received hundreds of such requests on many post-Facebook services such as Twitter, Foursquare and Quora. These new services offer a fresh start, a blank slate, a new skin, which I can use to define my present self for the people I currently care about. The old memories remain intact each time I undergo this digital molting process — I can always log back in to past accounts and find the people and content that were important to me at the time — but this personal collection of outgrown identities need not be central to my present self.

This does not necessarily mean that social web services are doomed to be left behind as repeated generations of users outgrow their old selves, and I can imagine features that would allow users to molt as they progressed through different stages of life. Facebook, for example, could have explicitly mirrored my real-life graduation from college on the site. They could have encapsulated all of my old data in an interface that was separate from my current profile and easily accessible to me and my friends from college, but not to all of the people I would meet in the future. They could have given me a new profile to fill out slowly over time, and perhaps it could focus more on my profession and less on my education. And they could have let me decide which of my old friends I wanted to re-add as friends for the next stage of life, and done it in such a way that there would be no social pressure to re-add all of the friends from my freshman dorm with whom I hadn’t talked in two years, since our college friendships would still be intact. I, as a user, would have gladly spent a few hours at my computer flipping through old memories and sketching the outlines for a new self, and I could see this feature as a coming-of-age ritual that people approach eagerly with pride.

People, and especially those who have not yet reached adulthood, will continue to molt their social identities as they grow and mature. Until services offer features that support digital molting, people will continue to shift their focus away from the web services they used to love.

Thanks to @ninakix, @christinacaci and @lehrburgerj for their help with this post!