Good

Anything that embarrasses and exposes governments is a good thing. Also, they say this endangers lives. Well, good. I hope those corrupt politicians' lives get endangered.

Furthermore, I only see one minor thing at http://en.wikipedia.org/wiki/United_States_diplomatic_cables_leak#Contents which would embarrass the U.S. government. I see countries aren't afraid to attack Iran, which is good. Comparing Mahmoud Ahmadinejad to Adolf Hitler is accurate.

• "Grave fears in Washington and London over the security of Pakistan's nuclear weapons programme." — That's reasonable.
• "Hamid Karzai being 'driven by paranoia' " — Well, most dictators are driven by paranoia.
• "Saudi donors remain chief financiers of militant groups like Al Qaida." — Well, duh. Most Saudis are brainwashed Islamic radicals. The only reason we're their ally is because of their oil. Personally, I think we should just conquer them and forcibly take their oil rather than paying them for it and making those terrorist bastards richer.
• "Iran alledgedy is in possession of missile derived from a Russian design and obtained from North Korea that are more powerful than any weapon publicly admitted to be in Iran's possession. These missiles, designated the BM-25, have a range of up to 2,000 miles (3,200 km)." — Why would the U.S. government even want to keep this secret? Iran and North Korea are our enemies, and the more the public knows about them, the better. It's also well known that Russia is selling its technology to unstable governments.
• "A Chinese contact told the American Embassy in Beijing that the Chinese government was responsible for instigating the January 2010 Google hacking incident. Chinese government operatives have waged a coordinated campaign of computer sabotage targeting the United States and its allies." — More information about our enemies' misdeeds.
• "Alleged links between the Russian government and organised crime." — Yes, we all know the Russian government is highly corrupt. Nothing to get all excited about.
• "Claims of inappropriate behaviour by a member of the British Royal Family." — Who cares? The British royalty are just celebrites and figureheads in government.
• "The United States apparently used bargaining to move prisoners from the Guantanamo Bay detention camp to other countries. In one case, if Slovenia did not take one of the prisoners, President Obama would not agree to meet with Slovenian officials. Other offers include economic incentives or even a visit from President Obama." — I can see why the government would want to keep this secret, but it only endangers the Obama administration's credibility, not the public. We deserve to know our government's lies and misdeeds.