So, let's look at some of the things that have been said about secrecy and the freedom of information. (And if that's too much for you on a Monday, you can instead design a new hairstyle for Assange.) First, what are we talking about? Depending on context, secrecy is sometimes called privacy, but fundamentally it's both the same: the deliberate withholding of information. If not only information is withheld, but it is replaced with faulty information, we'd be dealing with lies. But that's another topic that shell be discussed another time.
"True information does good."~Julian Assange
True information does not always do good, neither for the individual nor for the common good. Competition is an essential ingredient for innovation and progress in our societies, and competition is also essential for ecological and economical systems. But competition doesn't work well with leaking secrets, and even true information doesn't do good in the wrong hands.
Consider for example a company is doing a costly survey to better understand consumer interests, and then invests more money into developing a new product. If this information was shared with a competitor, the competitor would have the advantage without having made the investment. Thus, the company which made the effort would put themselves at a disadvantage by spending money on their studies. Here, the withholding of information is simply necessary for progress.
You can make a similar case for science. As discussed in this earlier post, if you invest time, effort, and money into designing and executing an experiment, you want to get something out of this investment: Be the first to analyze the data obtained, the first to potentially have a Heureka-moment, the one to maybe win a Nobel prize. If your 'true information' was publicly available from the moment you first saw it, what would be the incentive to do the experiment to begin with? What "good" would it do for science to prematurely share information?
Of course, competition isn't always necessary as incentive. The Large Hadron Collider (LHC), this decade's mammoth project, is basically without competition. Instead, it rests on collaboration. The insights that can be won are sufficient incentive in that case. But the LHC is not your average experiment, and whether one likes it or not, competition is a relevant driver of innovation.
"[I]nformation that organizations are spending economic effort into concealing, that's a really good signal that when the information gets out, there's a hope of it doing some good."~Julian Assange
The consequence might be that the organization just goes bankrupt. In general, it's somewhat inappropriate to call that "doing some good."
So much about Assange. Now let's look at somebody else's take on secrecy:
"If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place."~Google CEO Eric Schmidt
One of the most stupid remarks on privacy ever. There are many reasons people might not want to share some information with others. You might for example not want a prospective future employer to know about your health problems. You might not want your neighbors to know what you're doing on weekends, because you have zero interest in them chatting you up on your hobbies. You might not want your girlfriend to know you were arguing with your boss again, because she'll worry and get a headache and won't be in the mood tonight. Add your own favorite example. Human culture is complicated, humans don't always act rationally, and when to best share what information with whom is a context-dependent and non-trivial question. You don't want third parties to pass on information you'd rather have passed on yourself when time is right. Instead of doing good, it might just ruin your life.
"Information wants to be free."~Stewart Brand
Often cited, this quotation as it stands doesn't make much sense. Information doesn't "want" to be free any more than muffins "want" to be eaten. To be fair however, this sentence makes more sense within the context:
"On the one hand information wants to be expensive, because it's so valuable [...] On the other hand, information wants to be free, because the cost of getting it out is getting lower and lower all the time. So you have these two fighting against each other."
And indeed, leaving aside the rhetorical trick of assigning a will to unanimated bits and strings rather than admitting it's us who want information this or that way, there's two factors working against each other here and the ideal solution is thus neither extreme. It's as easy as this: Extreme positions are almost always wrong. Free information isn't always beneficial and information doesn't always do good, much like secrecy isn't always justified.
I would argue that the benefit of a piece of information to be publicized depends on the time and the manner in which it is being made public, and the best time and way is case-dependent. So there's no easy solutions and no catchy one-liners as answers.
But let's try and turn things around.
The necessary amount of secrecy tells you something about your society. If your government has secret information about other nations, it's an indicator for mistrust. If you don't want your employer to know about your health problems, it's because you suspect his opinion on your qualification will be affected. If you don't publicize your data before you've analyzed it yourself it's because you think your efforts won't be sufficiently credited. If you don't want a company to raise data about your shopping behavior it's because you're afraid you'll be swamped with ads.
In all these cases the need for secrecy arises because our societies are imperfect. Maybe, in an fictional world where ideas are credited where credit is due, where we'll all work together rather than compete with each other, where physical and mental conditions are perfectly integrated and not of disadvantage, where people don't have biases and all trust each other, in such a world true information might do good and therefore we'd want it to be free. But we don't live in this world.