Much like Chris Harrison's Bible viz, 140 Characters represents connections, or in this case mutual follows, with arcs. Employees are sorted by account creation date, and larger arcs represent an older employee linked with a newer one. The bar graph shows the number of tweets, relative to everyone else. For example, the engineers @al3x and @evan are quite active, along with newer employee @tiger. Good stuff.
140 Characters is meant only as something pretty to look at, but to take a step in the more analytical direction, I'd try sizing the bars by relative number of mentions between the employees. For one, you'd see who's most "popular" and second, you might start to see the conversations within the group. I'd expect @ev and @biz to have a lot of @mentions, especially during presentations. Placing employees by creation time, instead of just order, could be interesting too.