What is surprising about the study is how rapid and steep the dropoff rate is. Just moving from a common corridor to elsewhere on the same floor reduces the collaboration potential five-fold. This sharp dropoff in the effect of physical proximity is one more confirmation of a general result reported by MIT researcher Tom Allen in the late 1970s. Allen's study of engineers looked simply at the probability of communication as a function of distance between potential communicators. And, if there is no communication, there can be no interactions, no relationships, much less collaboration.
Large groups are by nature distributed.
Think of what it means to bring 400 or more people to one site. Work gets done in clusters. People at all levels work in and go to meetings with others in small groups. When a company goes about identifying the 400 people to be linked together into a new project, many will be recruited as part of an already existing small group, or part of a new working unit that is pulled together at a site with many other unrelated activities. Individuals may, of course, be attached to a network without functioning as part of a co-located small group.