I don't know about know, but I remember being told as recently as a couple of years ago that id Software used it as an inter-office chat tool. I certainly have imagined its use at jobs before, even when I worked in call centers. It couldn't be hard to let the rank and file chat when not on a call. (Yes, they were oddly draconian about doing nothing, or reading a book, between calls. Forget your book and your day is ruined.)