A couple of major platforms like Facebook and Twitter, YouTube, have become in many places around the world a de facto public sphere. Especially in countries that have less than free Internet, less than free mass media. And these countries have transitioned from a very controlled public sphere to a commercially-run one like Facebook.
With social media, the compelling opportunities for self-expression outstrip the supply of things we have to confidently say about ourselves. The demand for self-expression overwhelms what we might dredge up from the inside, from our true selves. So the self that we’re expressing in social media has to be posited elsewhere. We start to borrow from the network. We start to borrow from imagined future selves that we can project. We start to borrow from the media themselves and from other kinds of content circulating there that we can now constitute ourselves with.