Here is an excerpt from article written by Jon R. Katzenbach and Zia Khan for the Harvard Business blog. To read the complete article, check out other articles and resources, and/or sign up for a free subscription to Harvard Business Daily Alerts, please visit dailyalert@email.harvardbusiness.org.

*          *          *

Webster tells us that a peer is “one of equal standing with another” or “one belonging to the same societal group (that is, based on age, grade or status).” On the job, most of us have peers that we enjoy, respect and cultivate. We also have peers that we abhor, ignore, and avoid. Most peer interaction takes place “informally,” as there are no lines on an org chart that connect peers together

You might well ask, So what?

Peer to peer interactions may be the single most neglected lever of change. When enlisted, they are change’s most powerful ally; when resisted, they are its most stubborn foe. Peers in large organizations are invaluable in spreading behavior change across an enterprise. In that respect, they constitute a woefully underused set of resources, mostly accessible within the “informal elements” of our organizations.

Whenever significant numbers of peers interact formally or informally, they constitute a force to be reckoned with. When they share mutual respect, they will listen to, learn from, and secretly support one another in ways that can shape opinions, create resistance, or generate energy. Left unattended, their interactions may or may not be supportive of important enterprise priorities.

Look at high performing organizations like Southwest Airlines, Apple, FedEx or the U.S. Marine Corps, all of which rely heavily on natural, informal networks to keep peer pressures positive. The Marine Corps Gazette receives dozens of “letters to the editor” every month from ardent Marines who want to emphasize what it means to “live our values” versus display them. The Marines take their simple values (honor, courage, commitment) extremely seriously, and when violations occur, the Gazette hears about it — informally but compellingly. Similarly, any regular SWA passenger can attest to the informal networks that flourish among stewards, gate people and baggage handlers — it’s very clear that they take seriously their intent to make passengers feel good.

This is easier said than done — though elite military units, for example, and peak performing enterprises around the world have been at it for decades. In the U.S. Navy, for example, the informal camaraderie among Chief Petty Officers transcends oceans, continents and other geopolitical barriers; most of the time it is a force for wisdom, character and courage. In fact, it is interesting that some of the most powerful “informal” peer networks are found in command and control institutions. Sometimes, a peer network is the best way to work around a formal structure that gets in the way of getting stuff done.

*     *     *

Jon R. Katzenbach is a senior partner at Booz & Co. and founder of the Katzenbach Center at Booz & Company. Zia Khan is vice president of strategy and evaluation at the Rockefeller Foundation and a senior fellow at the Katzenbach Center. The two have collaborated on a new book, Leading Outside the Lines: How to Mobilize the Informal Organization, Energize Your Team, and Get Better Results, published by Jossey-Bass in April 2010. This is the first in a series of blog posts related to the book about the ways managers can lead outside a company’s formal boundaries.