The takeaway, happy or not, is that most companies see no disclosure as the only right disclosure and will punish you beyond reason if you're even connected to something that hurts them a little - even if they're the ones who caused themselves the hurt.
So, responsible for who?
Because the fastest way to guarantee this stops sooner than later is leak every address publicly with information about every error AT&T made and let civil suits from pissed-off customers fry them.
This is all just manufactured panic anyways so it's not like anyone would even get hurt. Email addresses aren't secrets and we don't act like they are or we'd be arresting spammers.
> That or avoiding these situation entirely by not meddling
No, then it'd still be broken and nobody would know.
> where you're not supposed to.
Sorry, but if you have my data or provide a service I need, I've got an interest in your systems.