Microsoft has somewhere near 100,000 employees, so cross-group communication is really important. Many senior managers have commitments that require close coordination between partner teams. Even in the smaller companies I’ve worked at, the most effective workers are the ones who can work across disciplines and group boundaries. In game teams, for instance, the partnership between the content creation team and the programming team is essential for creating a great title. How do you foster that partnership? The key is trust. People that trust each other create a 1+1=3 combo. How do you build trust? Through personal relationships. As Eric Brechner writes in One to One and Many to Many, personal relationships are built through getting to know people outside of a work context. That’s why things like work-sponsored "morale events" and conversations that involve more than just work-related topics are so important.
I think back to one of the most successful teams I worked on, and I credit much of our success to the fact that we regularly ate lunch together. Not every day, and not always the same group of people, but there was a regular lunch "train." We rarely talked about work over lunch. We talked about politics, family, values, travel, food, and games. The bonds we formed over sandwiches is what made it possible for us to get things done efficiently back at the office. Even more importantly, we could hash out disagreements about technology and still come away from the conversation as friends. We trusted each other.
Make the time at work and outside of work for people to form those bonds. That trust built from those relationships will pay dividends.