The probability of communicating or collaborating more than once a week drops off dramatically if people are more than the width of a basketball court apart. To get the benefit of working in the same place, people need to be quite close together. To put this in perspective, think of the people you regularly work with. Increasingly, the people we work with are no longer within shouting distance. Any team of more than about 10 or 15 people is, by sheer physical mass, probably more than 50 feet apart.
Global distance is another thing.
The further apart people are physically, the more time zones they must cross to communicate. Thus, time becomes a problem when people not in the same place need some of their activities to be in sync. Let s not forget, though, that people who work together in the same place can have problems being in that same place at the same time. Think about those in sales or consulting who rarely occupy their offices at the same time. These teams, too, often cross time boundaries and need to think virtually.