Yahoo could do that and include even all the emails their users 'deleted'.
At one time, back in the 'olden days, everyone operated on the net as if this was a very real possibility.
I work for one of the large ecommerce tech companies - we have some great devs and run a pretty efficient cdci pipeline, stuff ships fast. There are multiple layers of unit testing, automated testing, manual testing and peer review in place to prevent this sort of thing.
Despite that, I can totally see how it wouldn't take much for a changeset in one area of the site that affected the default option in a drop-down in another to creep under the radar.
Companies that don't protect unsophisticated users from simple mistakes or inaccurate mental models will get a reputation for being insecure and lose sales. This is regardless of whether the user "should have known better."
Whatever user groups they create are only ever going to be an artificial construct - it's all just lists of stuff