Wikileaks Speaks: What are the pros and cons of total, world-wide governmental transparency?

There is a huge uproar right now about the leak of some 90,000 classified documents about the Afghan war. It’s like the Pentagon Papers on steroids. And look for more to come. In this information age, which hacking and proxy servers and cloaking, how long till no government can be sure it can act in secret? And should that day come, what would be the pros and cons it would bring?