Look, there is certainly a role for a whistleblowing site and so on but it seems to me that there is not, a priori, something pious or beneficial about releasing any and all information. If someone put about your credit card details and PIN, would you applaud the transparency, for example?
Everything I've read from the dump of diplomatic cables might be titilating but I've seen nothing that would fall under what I would call whistleblowing and much of it is clearly damaging in some way or another.
In the wider sense, diplomacy is clearly best conducted with tact, delicacy and the frank exchange of information between diplomats on site and their bosses back at home. In the narrower sense, from what I understand certain sources in very unsympathetic countries have basically been outed by this information. This puts them at risk of personal reprisals and surely reduces the likelihood that people will provide information to the US in the future. Does this strike you as a good thing?
It seems to me that the only major indictment of the US that has come out of these cables is that they could be so widely accessed and so easily leaked in the first place. That does not justify publication.
It may be entertaining to read this stuff and, if you have a reflexive dislike of America, it may be fun to see their diplomats squirm, but really, what good has been done with the release? This isn't empty, childish rhetoric. This is real world, grown-up consideration of the value in what wikileaks has done. Fun != justification for releasing information. We might all like to know what is going on behind the scenes but any mature individual knows that some things are keep secret for a reason.