I'm not sure if you are in this demographic, but a lot of people I know born in 1999-2003 or so in the US used snapchat as a primary method of communication for many years, and a large part of it was keeping up "snap streaks" of sharing one photo a day with many different friends.
This is one thing for all of the pairs of genuine friends doing this, but I also have two friends who I introduced to each other exactly once, and who have never spoken since, who have a 6 year snap streak together, and both of whom have streaks like that with dozens of other people, many of whom are virtually strangers.
That is interesting. For a streak to count, do you have to both send out your own, and open incoming images? I wonder how much you could tell about someone if you had a 6 year snap streak with them. Would they be more like a friend, or an awkward relative with whom you seldom meet and have little in common?
Both of you have to send them to the other person as a specific recipient (so not just putting it on your story). I'm not sure about opening them.
For the two friends I'm thinking of, my impression is that they don't know each other any better through snapchat than they do from me knowing both of them and mentioning them to each other (they live 1000 miles apart and only met once). I guess the best I can say is that I would be comfortable seating them at the same table at my hypothetical wedding. Same vibe as my cousin I have on Facebook but have only really met twice in the last decade.
Well I knew someone who did this ritual and they would send black photos of their leg so close to the camera. So I'd imagine nothing and its classic number go up social media.