[brandonr49]

I will never get over the fact that the Nintendo Switch operated on random character strings to find friends rather than usernames or something more straightforward for normal users. But the fact that they managed it does mean it's not so large a barrier.

[lloeki]

I guess it works because people think of it as if they were phone numbers, plus it removes the barrier of having to choose a username. See also the now defunct ICQ which was fairly popular even outside of tech circles.