Obviously leaks that reveal actual wrongdoing are an unalloyed good. When the leaks that merely provide voyeuristic windows into the routine business of institutions (e.g. the diplomatic cables), the social value of the visibility becomes less clear. When leaks of that sort dominate, and consistently target American and western interests we have to question the motives and the integrity of the conduit.
Truth is power, yes, but is that power being granted to you, or used over you?