Privacy has to be viewed in the context of relative power. For example, the government has a lot more power than the people. So privacy for the government increases their power and increases the power imbalance between government and the people; it decreases liberty. Forced openness in government -- open government laws, Freedom of Information Act filings, the recording of police officers and other government officials, WikiLeaks -- reduces the power imbalance between government and the people, and increases liberty.
Without knowing the juicy details contained within the diplomatic cables that wikileaks got ahold of, it's hard to really know how good or bad it might be. There are things classified by the government that I'm pretty sure it's better stay classified. I'm going to decline to provide examples because apparently whenever I provide examples of this sort of thing, it makes people nervous.
But there's a lot of stuff in the Iraq war logs that wasn't really a good idea to leak. The Plame affair is another example.
Now, if you look at the characters allegedly behind the whole affair... I mean, honestly, neither Bradley Manning nor Julian Assange seem like the people you'd want to split a beer or a bottle of tequila with at the White House.
But, although it doesn't paint America in an especially good light, much of the contents of the cables is stuff that needs to get out on occasion.
On the other hand, this does tend to move the likelihood of 9/11 being caused by crashed airliners hijacked by terrorists and UFOs being people drunk/stoned/mentally ill towards the simplest possible explanation. Yet again, everything juicy will get out.