In one congregation, because a bro hadn't sign the form saying they could have his data, they wouldn't use his name or surname. So what he did some part on the platform, he was introduced as Brother Blank.
Maybe this is happening in other congregations. If so, even if they know each others names and addresses, they can't tell anyone unless the right forms have been signed.
The householders are probably safe, so long as they don't sign anything and ideally don't show any interest in the message.