Have you *ever* used BCC when sending an email?

Yes. In business communication, if there a bunch of people who are irrelevant to a subsequent thread, it is okay to put the excess people on bcc and say they can reply if they want to be added back in again. It is a really nifty trick I learned at a megacorp.

Yes, all the time. Imagine that Bob emails Sue and asks for help. Sue says, "I don't know the answer to this, but Jack does. I've CC'd Jack." And then Jack replies and says, "Moving Sue to BCC. Bob, I can help you with your problem..."

And now Bob and Jack can have a conversation and Sue doesn't get flooded with responses that she's no longer interested in...

At our company, people use it when they send all-staff messages. The all-staff group address goes in the BCC and the person usually puts themself in the To address. This cuts down on the useless Reply All "thank you" and "me too" messages going back to all staff. There are other ways to prevent that, but this has been one of the few legitimate and above-board uses of BCC that I have come across.

For an email to a large of group of people where you don't want to disclose everyone's email address, BCC works well.

Regularly.

I'm managing registrations to dance lessons at our club.

If we need to tell the participants something, I send out mails with From: ourclub, To: ourclub, and Bcc: all participants.

We're not disclosing mail addresses to strangers who just happen to take the same lesson.

I find this comment thread very funny - OP asking for support of his view and gets crushed by the fact that this is an often used useful feature.

I had a fresh-from-uni junior who asked why the hell I put some people in the "to" field and others in "cc" it will be the same result, everyone listed will get the mail. So why bother?

Yes, maybe 4 times per year. Probably should do it more. I receive BCC'ed mail more frequently, but that frequency should be higher. There should probably be a feature in Outlook that stops and asks "Are you sure?" and makes you wait 30 seconds when replying-all to anything more than 10 people. Maybe the wait should be 1 second per recipient.

All the time, when "smart ass" customers try to pull up a move, I always BCC their boss.

Yes, consistently. I have two primary use cases:

1. Drop copies of things I want to be absolutely sure I have access to, into a source controlled by me without broadcasting that fact. It is super easy with BCC

2. Notify people of a conversation without involving them directly. Usually, this means getting advice, or giving a heads up, should they need to be involved later.

Funny you should ask, at my work this was a recent source of tension because a culture had emerged of people using bcc to silently keep others apprised of tense email exchanges — so that someone would have seen the exchange before gossip went around, for example

Yes, but I only BCC myself. This it provide me with a 'CC' of the mail to ensure that it left me OK. It's also an alternative backup if things go wrong.

In fact, my mail client is setup to automatically BCC all mail I send.

Yes - it’s useful to avoid disclosing the identities of recipients to one another.

Yes, very often I will BCC: my personal email from work with HR/benefits related conversations or praise from a boss or customer I want to save.

Certainly, for all-staff messages. It prevents reply-all storms.

Yes. Copy HR on things I need to document or otherwise remove people from a thread.

Useful for some email filing systems.

I bcc to log my emails on Salesforce

yes. usually for people submitting a form in google sheets, and replying to all via BCC

yes, for all the reason that everyone has already listed.

Yes

Yes