Interesting I didn't know that terminal sessions were files. So if I was root on a shared host, I could theoretically hijack and listen to what other people are doing in their SSH sessions.
You might also find the man pages wall(1) and write(1) (That's the terminal utility write, not the syscall write(2).) interesting.
(Edit: well, actually, if you're SSH'd into a remote host, your terminal emulator is probably local, so you might not be able to see into its memory unless you're root locally, ofc.)