Do ask; don't lie.
(Rationale:) How can we find the happy medium between disclosure and prying, between transparency and overexposure? The last thing we want is a law saying that everyone should disclose everything: vested interests, negotiating strategies, intentions, bank account, marital status, whatever.
How can we instead devise some rule that fits the best qualities of the Net decentralized, more or less self-enforcing, flexible.....and responsive to personal choices? The idea is to create a culture thatexpects disclosure, rather than a legal regime that requires it. People can decide how much they want to play, and others can decide whether to play with them.
First of all, it's two-way. It's not for a single person; it's for an interaction. The first person has to ask; the second person, to answer truthfully or refuse openly to answer.
It drives the responsibility for requiring disclosure down to where it belongs - to those most likely to be affected by the disclosure. It decentralizes the requirement and the enforcement to everyone, instead of leaving it in the hands of a few at the top. (If that's an awkward use of "requirement," it's because we don't even have a word for "decentralized command.")
As an individual, you are not commanded to answer; you may want to protect your own privacy or someone else's. But if you do answer, you must do so truthfully.
Then it's up to the people involved to decide whether to engage - in conversation, in a transaction, in whatever kind of interaction they might be contemplating. The magic of Do ask; don't lie is that the parties to any particular interaction can make a specific, local decision about what level of disclosure is appropriate.