I recall that on the Dynix (Sequent?) and SunOS lab workstations back in college (early 90s), users' TTYs had pretty open permissions. One could echo a message and redirect directly to your buddy's TTY. Also good for blasting annoying users from their session -- cat'ing binaries or chargen output was often enough.
There's something to be said of the old-school wonder of fingering random machines on the internet (say, from one's email bang path) for logged-in users then initiating talk sessions.
There's something to be said of the old-school wonder of fingering random machines on the internet (say, from one's email bang path) for logged-in users then initiating talk sessions.