It's apparently a basic rule of information hygiene that you can't ignore classification just because something becomes public, so, ignoring the fact that data is classified may demonstrate to a prospective employer that you don't understand how to take classification seriously.
I can sort of see the logic: if you are working for an organization whose classified data got leaked, but the organization has not declassified that data, you must still treat it as classified to avoid leaking any other related data by accident (for example).
But these students don't work for the government yet. Discussing leaked cables does not necessarily imply they don't understand classification.
That is not quite the reason. The real reason is that those who have clearance can be prosecuted for a willful security violation if they:
* store, process, or view classified data on an un unauthorized machine (home laptop)
* grant others access to the classified data
* discuss classified information where others who are not authorized would overhear or see it.
* prying into or accessing classified info for which they don't have a need-to-know
* creating unauthorized copies of classified info
The warning not to access this info is basically a helpful tip or reminder so those who hold or will hold clearance could be subject to harsh penalties.
This is just as much about protecting the classified info as it is the protect those who have a clearance.
These rules and laws have been deliberately written to be broad and wide so that a potential spy can be easily prosecuted as they are usually found in possession of classified info in their house or on their laptop for which they have no authorization to have.
There is simply no exception for the case when thousands and thousands of classified docs have been spread over the internet and are just as easily accessed as driving directions to a restaurant.
EDIT:
This is actually a great example of how a broad and overreaching law (by virtue of not being updated to specifically exclude leaked info) can be used to selectively prosecute certain individuals at will. Chances are some of those who have a clearance have read excerpts from Cablegate on the web just by reading the news. An overzealous prosecutor can turn that into a "willful security violation" if they really want to. This is in the same category as "obstruction of business", "obstruction of justice", "disruptive behavior" charges.
But does that standard make sense applied to private citizens, having conversations about widely-available information, before ever applying for a job?
The State Department may get more careful, coldly calculating applicants by eliminating those who discuss leaked cables – but not more curious and well-informed ones.
EDIT: In case it wasn't clear - I am calling the policy asinine, not the employees/contractors.
I always figure that at work 100% of what I write can be read by the entire company, and that I will be held accountable for anything I say/do even if I have the best intentions in mind. If I say in an email something unfavorable or slanderous about another company's CEO, and it gets out, then I must face the consequences.
It seems that American government employees and diplomats have another expectation of privacy and consequence to what they say/do.
The key difference here is that making honest assessments about the character of foreign government officials is part of the job description for diplomats.
Some jobs have risks associated with them. This is one of them. Time and time again our government has told us that we are made safer by having less privacy, but now when it comes to the government having less privacy, they don't like that feeling.
In either case- why wouldn't what is said and done by diplomats carry consequence? Politicians always talk about responsibility and accountability. This seems to be a ripe time for it.
From that point of view, it only makes sense to assume that the screening process will be more strict moving forward. No surprise, then, that one metric that may be taken into account will be a person's feelings toward Wikileaks. I imagine the people conducting clearance reviews will look at everything a candidate has posted online, and ask them directly how they feel about Wikileaks.
Sympathetic feelings toward Wikileaks is simply a chance the US Government will not be willing to take.
Especially considering that a big part of what's been released so far has been ho-hum stuff that just reinforces what a lot of people have speculated was true---"Eh, they don't really think that'll work."---and now making a comment like that means you're propagating classified information and thus ineligible for a State Department job?
I mean, it has shades of the old Khrushchev line ("3 years for insulting the premier, 20 years for revealing state secrets.") It's one thing to say that a leak that one person saw does not automatically declassify something (trade secret law works the same way), but when the leak is on this kind of scale and has been commented on so publicly, it seems hard to justify.
By contrast, restrictions would make sense for current government employees. Because a significant fraction of those employees have access to materials whose secrecy is still intact, it is conceivable that discussion of the already-leaked materials could lead an employee to let slip additional classified information.
