Security by obscurity means hiding the algorithms, not the keys. In this example account numbers, etc. are the keys
Unfortunately, it is how most of the banking world right now works. It is quite easy to initiate transactions and create accounts knowing a few basic numbers about you - bank account numbers, name, date of birth, SSN number (I'm talking about the US of course), home address. And it is very hard to change or hide many of these numbers and data items. The system is very fragile right now, and the only reason why it works is that overwhelming majority of users aren't crooks and losses from the crooks are small enough to be covered without triggering move to a more resilient system.
So freedom of speech is only morally necessitated if it's deemed to be in the public interest? That sounds like you're setting a restriction on speech.
If something is in the public's interest, it generally makes sense to disclose it to the public.
For example, if a car manufacturer (or bank) makes public claims that their system is secure, yet they use 56-bit DES keys to encrypt data, then I think the public should know.
Your "account number" analogy was off because it's is generally not in the public interest to reveal a private citizen's account number.
However, if an account number (email address or ip address) was being used frequently to commit crime, say in an advance fee fraud, then it makes sense to blow the lid on the said account number. That's what I meant by "in the public interest".
Yes, it was a rhetorical question meant to illustrate that there are some things for which it's not evil to publish. Another example would be the names and locations of victims of spousal abuse that are in refuges.
In any case, if you're being that pedantic, why didn't you notice that I actually asked revelation that question, and not DJN?
Security by obscurity is flawed.