This question is motivated by the comments on this answer: https://buddhism.stackexchange.com/a/1354/28
Is it our responsibility (where "our" refers to the users of this site, including moderators and employees of Stack Exchange) to maintain the secrecy of texts that are not published and have been deemed unsuitable for public dissemination? If we see a text being disseminated that we think or know should not be disseminated, should we remove the offending content?
There is an obvious parallel here to an oft-discussed topic on the technology-related parts of the network: Should moderators enforce NDAs for software vendors?.
I won't rehash everything that is said there; the basic gist is that no, it is not the responsibility of anybody here to enforce NDAs (or other secrecy agreements), since none of us (besides, perhaps, the user that posted the "offending" content) are bound by those agreements.
Now, this isn't to say that people shouldn't be judicious about what they post. If a teacher of yours has taught you something and sworn you to secrecy on it, you should probably not post that thing, as a matter of basic courtesy to your teacher.
I agree with what @senshin has said about this topic, but wanted to add a few more points in the areas that go a little beyond the NDA-analogy.
What this implies is that one shouldn't share information that the one who taught them considers oathbound and shouldn't seek information that their instructor considers oathbound. Circumventing those sorts of restrictions is generally at least rude if not in violation of a pact or agreement, and minimally should be discussed with the instructor in question.
On the other hand, it isn't incumbent on others–nor is it really practical–to enforce keeping such knowledge hidden or even to discourage people from asking.
The difference between NDAs and religious esotericism is a matter of cultural respect - NDAs don't offend something people take personally. We could ask a parallel question of whether we should allow posting of pictures that denigrate the Buddha. I would say if any material were found offensive to practitioners of Buddhism, we would be obligated to remove it, no?
In some ways religious esotericism is similarly about respect. I know that there are some few teachings in my tradition (mostly technical details about intensive meditation courses) that we try to keep from new meditators so they don't misunderstand what they aren't ready to hear. If such teachings became public knowledge on the Internet, I'd want to request their removal, because I would feel it would hurt peoples ability to practice my tradition sincerely. I'm sure other teachers feel similarly.
That being said, the Internet doesn't really lend itself well to secrecy; so the question, I think, is whether we feel obligated as a community to respect Buddhism, or whether we are just here to study it impartially.
My feeling is that, since SE does have policies on disrespect, we should at least consider that it might be disrespectful to post teachings that are intended by teachers to be kept secret.
I suppose another difference between NDAs and esoteric teachings is that NDAs deal with a desire to possess something exclusively, whereas esoteric teachings are for the purpose of preventing abuse; they're not really as parallel as they seem at first blush. Esoteric teachings are more like intellectual property, in the sense that the teacher may be seen to have some right to control how they are spread.
td;lr: I'm of the opinion that, out of respect for individual teachers, we consider a policy of responding to requests to take down esoteric teachings by those who consider them esoteric.
This should be treated like spoilers to popular movies.
For example, here is the top level tantra, the one you get just before you're enlightened:
(only highlight or mouse over the text below if you have suitable Abisekha!)
Nothing really exists like you thought it existed.
The mark down syntax is to start a line with >!
I would say that the problem with secrecy is a bit more subtle, at least in Vajrayana tradition. Once a student receives some teachings and instructions, so-called Samaya is being formed between him and the teacher. A student promises to keep a number of vows and commitments. One of the ways to break the Samaya is to 'Reveal Secrets to Those who are Not Spiritually Mature' (point 7 in this list). Internet is a public space, so there is a risk that people with not enough spiritual background will read some teachings and misunderstand and misuse them.
There is also a nice guide to using social media for Vajrayana students, but I would risk to say that some of the points are relevant to all the practitioners.
I think that it is ok for the community to challenge users whether their answers contain teachings that should be kept secret. If someone reveals secret instructions, I wouldn't call that person an expert as he/she lacks the basic understanding of the meaning of the teaching he/she received. We want a quality site about Buddhism which we respect and want to protect.
Practically, I would suggest to include some guidelines either in FAQs, community Wiki or similar to remind the users about the meaning of the secrecy so they can reflect on whether they do protect their lineage. It would be also beneficial for non-Buddhists users visiting the site so they can learn why, for example, nobody wants to answer certain questions in great details.
In Buddhism there is not secrecy involved. Anything which is within the topic of this site cannot be a secrete. Also this all the topics would be an adaptation of the original teachings of the Buddha and his disciples and in some cases founders of certain schools of Buddhism. So anything unpublished if need to be kept secrete will not likely conform to the topics of the site and it does not draw upon the knowledge which is already publicly available in some form or other.
