Charles Miller at the Atlassian Developer Blog – Agile Context Switching with "The Disturbed":

"Programmers, the authors proposed, are at their most efficient when they reach a state of 'flow' in which they are able to concentrate fully on a single problem. Any developer will tell you how satisfying it is to be in this state, how productive it is... and how easy it is to be pulled out of it by the smallest interruption. What's worse, since it takes at least fifteen minutes to reach this level of concentration, any interruption no matter how small can cost you a quarter hour's productivity. A constant stream of small interruptions, say a phone near your desk that rings just twice an hour, can make a developer unproductive (and miserable) for most of the day.

Our solution […] was to designate a single developer to be "The Disturbed"; taking a two week stint to act as a magnet for all the questions, requests and distractions that would otherwise be distributed across the whole team. […] Because the Disturbed isn't expecting (or expected) to get much of that work done while being disturbed, it is far less frustrating for the developer and far more predictable in terms of scheduling and estimation for the team as a whole."