Snapchat's Ladder
stratechery.com/2016/snapchats-ladder
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Moreover, the primary means of communication was not text but rather a picture, usually a selfie. Again, this more closely corresponded to how people actually communicate — non-verbal communication with our face is even more important than verbal — and also appealed particularly strongly to teenagers: while everyone is ultimately mostly concerned about themselves, teenagers don’t even bother to pretend otherwise!