Why would any foreign national cooperate clandestinely or covertly if they know that the US government can't prevent these leaks?
When this type of information is leaked out, it will hurt future recruitment and cooperation efforts.
US Government: We want you to work with us covertly
Foreign National: But I am afraid of the risk to me and my family.
USG: Trust us, we will protect your identity and your relationship with us
FN: One word "wikileaks"
USG: I guess our conversation is over huh?
The jerks who work for Wikileaks do not have a legal obligation to protect sensitive information. Evidently they don't care at all about the moral issues.
However, somewhere there is a person who, via their NDA, has the legal responsibility to protect this sensitive information. And they have violated their legal and moral obligation. These are people without honour and we need to find them.
How anyone can voluntarily sign an NDA, garner all the benefits from the position of trust (accepting the queen's shilling, as it were) and then betray that oath of honour? The only conclusion I can make is that they are devoid of honour and have no concept of being a professional.
I have nothing but disgust for these scum and I hope they are caught and punished for their betrayal.