Maybe Snap will stick around and maybe it won't but I've already found myself reaching for snap to send an image of a restaurant instead of typing it, or sending a reaction selfie instead of an emoji because its so much easier than typing.
RFC 7, from May 1969, used it: https://www.rfc-editor.org/rfc/rfc7.txt
Regardless, it's certainly an old habit
Or maybe the same convention might have even been used before typewriters, to mark up manuscripts? (A manuscript needs clear instructions to the typesetter, because someone’s handwriting might not make the distinction between Roman and Italic scripts immediately obvious.)
I think the biggest place where facebook fails, is making it easier to segment people and create groups.
Where you can easily setup a group, of say friends, and you can more openly post. Without telling grandma about how you dropped LCD at the concert two days ago and had a wild time.
You _can_ do this now, but it's clunky and painful.
^badjoke
It might slow migration from Instagram to Snapchat, though.
But then, I started _really_ using it, and something clicked. Snapchat enables serendipity in the digital world. Unlike traditional social networks, where people curate their image, limit the amount they post, and where a smart feed decides what you see, on Snapchat people post unfiltered real-time snapshots of their lives, and when you go through the story feed, you see everyone's content. Snapchat makes it dead easy to reply to stories by just swiping, and unlike a public comment on other networks, it goes straight into their chat inbox. That makes it really easy to start conversations about things actually going on in people's lives. It's the ultimate ice-breaker.
Thanks to that ability to super easily and non-awkwardly talk to people, I've become friends with people who would otherwise be strangers or merely acquaintances. I've had relationships and flings with girls that I only talked to because it was easy on Snapchat. (No sexting involved.) That effect is what makes Snapchat truly special and different than other networks.