After wikileaks spread the US cables, Hillary Clinton said something along the lines of “this is bad for International diplomacy”. I think she’s right.
Diplomatic resolution (as opposed to violent resolution) of conflict requires trust, which is undermined by this leak.
Also, some information is not meant for public consumption. Pin codes are in that category; security/police information; a list of worldwide targets that are important to the US/global security/economy that may be of interest to terrorists (now on wikileaks) also fits that bill.
Someone somewhere wrote that if the internet/wikileaks existed during the time of the camp David accord, it would not have succeeded. The idea that any and all information, be it government related or not, should be available to all seems either naïve or scarily fundamentalist to me.
That doesn’t mean that there aren’t things that are important and relevant for the public to know: Some Arab states asking the US secretly to be harder on Iran, while in public being all cosy with Iran and critical of the US, is questionable to say the least.
I think whether such a leak is ethically right or wrong depends a.o. on the contents of what’s leaked: It has to show greater wrongdoing than the wrong that leaking it represents. And the effects have to be taken into account: Are they positive or negative in the long run? Both are of course highly subjective judgment calls.
Thomas Friedman had an insightful column about wikileaks, in which he argues that the US lacks leverage on the geopolitical scene. He writes:
America lacks leverage in the Middle East because we are addicted to oil. We are the addicts and they are the pushers, and addicts never tell the truth to their pushers.
We also lack leverage with the Chinese on North Korea, or with regard to the value of China’s currency, because we’re addicted to their credit.
(based on my comment at Stoat)