When I worked at Ingenta I installed an instant message server and gave everyone in the company an account. I also automatically created everyone's "buddy lists". The buddy list contained everyone's account (in one list ordered by first name), it was fixed (no adding or removing accounts), and was updated with every staffing change.
The server was a great success -- over time. Even the COO logged in each day. Over the course of my work day in Providence, RI (US) I would see the Providence staff's full work cycle of starting their day, going to lunch and coming back, and ending their day. For the Oxford and Bath (UK) staff their day had already begun and so I would mostly see them return from lunch and end their day. For the lone California developer I saw him start his work day just before I headed out for lunch.
And it wasn't just me that saw this but everyone because everyone had the same buddy list.
Read Geoffrey Bilder's posting, "Backchannel" , about his experience at Ingenta.