It is expecting that if large power structures (governments, corporations, institutions) are afraid their dirty laundry will be exposed they will try to act more responsibly. Well, perhaps in reality they will just try harder to hide the dirty laundry, but that's for another discussion. Going with the original idea, if coalition forces in Iraq and Afghanistan feel that what they do day to day could end up on Wikileaks.org, perhaps they'll think twice about tolerating or engaging in abuse. Anyway, I think that's the logic.

Now you can of course ask "What did Obama do to deserve the Nobel Peace Prize?". My answer would be "nothing" but many here will probably disagree with that. So to me it all just seems rather random who gets peace prizes and why: Is it a statement of encouragement, like a "preemptive" peace prize, in hopes more peace to come in the future? Or is it for specific past accomplishments, and then how does one measure that? What were Obama's accomplishments when he got his?