Going to the companies who have to validate user passwords to get a password a user is unwilling or unable to divulge is wrong. Going beyond that in asking for details on how passwords are salted, hashed, what the salts are, etc. ... more wrong still.
That the practice has been revealed should be all any internet startup/company/organization should need to never, ever store a user's password again. Ever.
Where compelled disclosure of a password falls on that spectrum is, indeed, a matter of debate.
However, this is not the same. This is compelling a company to turn over either a user's password (which the user [debatably] could not be forced to turn over without potential infringement of 5A) or specific technical details necessary to business, security, and privacy operations to help them decrypt an encrypted password.
My examples were specifically not about compelling a person criminally charged or investigated to divulge combinations or produce keys. It was about compelling the safe-makers and key-makers to do the job as an end run around users being unwilling or unable to provide the demanded result.
Tangentially, this revelation makes me think a bit more about the CISPA requirements that were discussed regarding protecting employees from being forced to surrender passwords to their employers. Can't help but wonder if backdoor conversations on that proposal were engineered by executive wishes to be able to compel employers to turn over employee passwords because they haven't been successful with service providers directly.
[edit: mixed up my former/latter statement. added last comment. fixed spelling/grammar mistakes.]
If not, then to me it would seem that the only password that could be compelled is something like a hard drive firmware boot password, where the contents may not be encrypted but can't be accessed (through normal means) without the password.
Saying "turn over the physical object used to commit crime" makes turning it over testimonial! But saying "turn over the rifle with the serial number 98980843" is not testimony.
And even then, a password should be encrypted. If there is a court order to reveal information, then there has to be a way to get this information rather than sending unencrypted passwords to the government so they can snoop through your mail without even being proven that you are guilty.
I must point out, "snooping through your mail" requires probable cause, not proof of guilt (that's for a court to decide).
In what ways is it in a different category to their phone company handing over their call logs and getting someone to impersonate their voice (or send a text message) to an associate?
A single password, in an active situation, with oversight [2], is a totally different proposition from something like Prism or handing over SSL private keys.
[1] Not sure about US law on entrapment, but "bring the kit, we're doing it tonight, rendezvous is XYZ" and then seeing who turns up with what doesn't sound like entrapment to me.
[2] I have no idea what oversight might or might not be applied. "No comment" from the government is admittedly not an encouraging sign.