Public discussion of the subpoena of telephone records of Associated Press reporters as part of a leak investigation has been impaired by widespread ignorance or misunderstanding of what is going on with this case, as well as by the political environment in which the issue has surfaced. To begin with, none of us on the outside have any good basis for assessing the importance or potential importance of the phone records to this particular investigation. We don't know what other leads the investigators have, and we don't know the breadth of follow-up implied by whatever leads they do have. We thus have little or no ground as uninformed critics for second-guessing how the FBI is handling the case, in terms of obtaining the records at all or of the extent of the records that were subpoenaed.
The damage of leaks appears to be widely misunderstood, given how swiftly many commentators are brushing aside the issue of damage in the current case. Leaking of classified information significantly harms national security because it is awfully hard to run an effective national security operation if what stays secret and what becomes public is determined by any individual with an ax to grind or a personal agenda to push and enough of a wild streak to break the rules. Some commentary has offered opinion on how much the particular leak that is apparently in question in the current case was or was not damaging, but that is too narrow a perspective. Any leak is a blow to the discipline needed to keep secret information secret.