I can see it being wrong in circumstances, but I don't think just because the government has deemed something confidential should make it wrong and/or illegal, confidentiality != underage (and I'll assume you mean child rather than, say an 18 year old) alcohol consumption. The classification doesn't matter, it's the content. What wikileaks is doing is far different than publishing a list of people in the CIA, FBI, and Witness Protection Program along with their addresses and family's addresses.
Edit: furthermore, I'd like you to consider the case when our own government's illegal action is exposed. Do you really think it should be illegal to reveal the illegal actions of our government?
To answer your edit, how did you find out about those illegal activities? It's like saying, I have to break the law to save the law. There are probably things that the public should know about and things that the public should not, however, it should never be up to 1 man to decide which is which. Until such time as we correct the situation that we are in, we still have laws and morals to follow, and spreading confidential documents of whatever caliber belonging to the government is still wrong. It's a round argument I know but two wrongs never make a right.
You're still under the assumption that illegal is immoral (or that exposing secrets is in itself immoral). If the government were to disclose the hypothetical lists above, unclassified, would it be right to print them everywhere? (And in fact when the government "accidentally" reveals identities no one is really prosecuted... http://en.wikipedia.org/wiki/Plame_affair see esp. Libby )
I agree, it should never be up to a government man to decide which government secrets the public can hear about.
If the government wants to assemble a non-governmental board of oversight that's immune from interference from the government, and that will inspect every secret document available, evaluate if the public would benefit from hearing from it, and release it if they think it's in the public's interest (no matter if government agents ends up shamed, imprisoned, or just disagree), I'm all for it.
Governments have proven for the last several thousand years of history that they do not give a damn about laws and morals, and will do whatever feels expedient in a certain situation, irrespective of anyone getting fucked over, killed, silenced, or otherwise harmed in the process.
Edit: furthermore, I'd like you to consider the case when our own government's illegal action is exposed. Do you really think it should be illegal to reveal the illegal actions of our government?