I have grumbled before about the trend away from private offices towards cubicles and open plan offices. At the same time, there are people who genuinely prefer these offices, which I considered inhumane. Then I read a book: "Quiet: the power of introverts in a world that can't stop talking", by Susan Cain. It helped clarify the differences between introverts and extroverts, the rise of the latter, and the implications all this has on workplace productivity.
Cain's definition of introversion and extroversion is pretty much what you would expect if you are familiar with Myers-Briggs. She emphasizes that "introvert" does not mean shy nor anti-social. Rather, an introvert tends to focus on the inner world of thought and feeling, enjoys solitude, dislike conflict and focus well. An extrovert would be the opposite, focusing on the exterior world and social interaction, are comfortable with conflict and enjoy multitasking. Another way to look at this is to say that introverts are more sensitive to outside stimulation, such as noise or people, and thrive at lower levels of such stimulation. Conversely, an extrovert needs a greater intensity of stimulation to feel "right". An introvert needs solitude to recharge after experiencing elevated levels of stimulation. An extrovert is the opposite: he recharges with social interaction.
The difference between introverts and extroverts -- keep in mind this is a continuum rather than a binary distinction -- in terms of optimal stimulation levels helps explain work environment preferences. An introvert works best in a relatively quiet, distraction-free environment, such as a private office. An extrovert is energized by the constant social interaction of pair programming and the bustling activity of an open plan office.