An interesting result:

Susan Fussell, Sara Kiesler, Suzanne Weisband, Peter Scupelli, and Leslie Setlock are conducting laboratory studies of the effects of distance on managing multiple projects. They have discovered that when people are engaged in two separate tasks with separate partners, they will tend to favor tasks with nearby collaborators.

Fussell, S. R., Kiesler, S., Setlock, L. D., Scupelli, P., & Weisband, S. (2004). Effects of Instant Messaging on the management of multiple project trajectories. Proceedings of the ACM Conference on Human Computer Interaction. CHI ’04. (pp. 191). April 23-30, Vienna