What changes to cause dedicated employees to betray company confidences?  What causes patriots to commit treason?

Many organizations have policies on the sharing of non-public information.  What changes within an organization’s culture for its employees to betray confidences?  What changes within a one-time dedicated staff member to rationalize the sharing of such documents?

The illegal disclosure of documents published on Wikileaks is an extreme case of inappropriate disclosure, one that can damage relations between governments, cause wars and one that puts a great many lives in danger.  What I would like to examine is the transformation of committed staff into a secret enemy of the corporation.