i was reminded the other day of a certain provider who about 7 years ago sent out a mass message to all her past clients and prospects . about 150 of them ... how do i know how many .. because she didn't BCC  ( blind copy)  the email addresses   oops !!    while some emails were like  [email protected]    others were guy's email life corporate names   double oops!  for all to see  

But yeah that's pretty bad.

Because I was on the receiving end of such an email. I saw on the CC a shit load of email addresses, figuring WTF.
Not sure if its the same one you're referring to.
It was from some chick in Vegas

Dallas babe

My experience was much less egregious.  
My favorite provider was retiring and moving overseas.  Since she wouldn't be readily available to answer reference requests she broadcast her "approved" client list to the local girls she networked with. She didn't ask or tell me who received her list.

I would never share anything without permission.

Was advertising BB when it was taboo.,,?

Major oops but not surprising. While interacting with other providers (social media/giving or receiving references) we also sometimes see unprofessional practices, or what we consider discretion breaches. Hopefully it was a mistake? Not justifying it.. but what comes to mind is they were testing a new method to send a newsletter, or a newly hired assistant who didn’t understand the assignment.