I'm not sure that's what's going on, though. Certainly, there are restricted ceremonies, especially involving initiation, and dangerous names with magical power. But more relevant seems the fact that much ceremony is performed for or at least in the presence of people who don't understand it. It might be designed for misunderstanding, with an exoteric and an esoteric levels. But with time, it seems likely that many who aren't permitted to know something might nevertheless come to understand it. (This explains why the last surviving members of some clans have shared with ethnographers, linguists and historians knowledge far beyond that which they were, when all was still well with their society, allowed to know.)
This is not a problem, as I understand it. It is not a problem because understanding - or even becoming acquainted with - something isn't the point. In Aboriginal cultures, stories, songs, dances, artistic patterns are not things which are known but things which are owned. I have no right to repeat a story I hear, unless the teller (assuming s/he is authorized to tell it in the first place) gives me permission. (Indeed, in Yolngu society at least, there are three kinds of right towards a piece of cultural knowledge: rights of ownership, managerial rights, and rights as guardians.) But that doesn't mean I don't hear it except when authorized to use it. In fact, I suspect most of what you hear and see is stuff you're not entitled to make your own - and that thus much "sacred-secret" knowledge is, in our terms, widely known. "Secrecy" here is not about hiding things where others can't encounter them (and where a secret can be spoiled forever through exposure, even by accident) so much as a system of property (which maintains itself). Meanwhile knowing something is having a responsibility to it - to maintain and not to squander it. And all the while you trust that others, who have rights to things you may or may not know, will discharge their responsibilities to what is theirs (which is really their part of what is all of yours).
The idea of knowing (in our sense) things you have no right to is an intriguing one. In a way it's not that different from being told something in confidence: you can't use - retell - it, as it's not yours to tell. I suppose we all carry around with us secrets of this kind all the time, and that some of them aren't really secret - in the sense of unknown to others - at all. A good person keeps secrets. But is it a good society that needs secrets at all?
I'm part of a culture of secrecy: academia. Peer review, faculty review, searches - all these involve knowing things you can't use. I remember, during my time at Princeton, discovering that people who I thought knew little of me in fact knew a lot about me - all the faculty, I learned once I became one, were tracking the progress of all the graduate students in the department, not just those in their subfield. And the same went for junior faculty, about whom more senior faculty learned things the junior faculty might never learn about themselves. Being on the more senior end now, I sometimes find myself in possession - well, the Yolngu case would suggest, precisely not in possession! - of information about people, sometimes people I know well, which they may never know I know, and some of which they themselves will never know.
This is hard. It's unsettling to consider that others possess [sic] comparable knowledge about me, and actively unpleasant to feel myself bound in confidentiality to other senior people whom I don't like at all. I'm learning that this discomfort is one one can live with, however unhappily. (I'm not talking about possible injustices in review processes, but something more essential to the system.) I see its point in academic life, but have found myself wondering whether the same adjustments are how societies - even or especially unjust societies - survive. How you make and maintain a ruling class not just by shared benefits but by restrictions on speech: like it or no, there are things I can't talk about with people I care about who are below me in the tribal ranking - things they can't even know I can't talk with them about. Meanwhile, I can if I wish talk about all these things freely with others at my level. We may not like each other, but we share much knowledge, and, as importantly, the experience of not being able to share it with people we like more. Willy nilly, affective relationships are being restructured, solidarities shifted, hierarchies embodied.
Is it naive of me in a Habermasian way to think that there must be ways of living with people that don't depend on the powers of embodied secrecy - that transparency in all things (if not perhaps at all times) would make for a better, freer, more fully human society?