Pittsburgh Tribune-Review columnist Salena Zito identifies another way in which leaks hurt our ability to gather and analyze intelligence:

In some cases, the information we have depends on entities or people giving it to us or cooperating with us. To the extent that information is compromised, it can determine what people decide to give (or not give) our intel community. Think of it in these terms: If you’re an analyst and you have information that is important and sensitive, you may be reluctant to circulate it if you’re afraid it will leak. Thus, important information can remain in a “stovepipe,” unshared. As one senior government official told me, “If there is a perceived breakdown in discipline, the danger becomes (that) we will see an open season on secrets. Leaking may beget leaking.”

“A perceived breakdown in discipline” pretty much sums it up.