If I recall correctly, the church maintains a data base of it's members.
Well it depends what you mean by data base. Can you explain this?
There are likewise, email lists for each Ward and Ward directories accessible by membership ID numbers.
No there are not any such lists. Members can, at their option, access the LDS Church member website. To do so they need to set up an account. They need their confirmation date and record number to do so. They can, at their option, give their email address and select what distribution lists they want to be on, such as stake or ward calender event distribution list. That is is.
It wouldn't be too hard to "out" someone as a doubter or apostate to friends and family in the local Ward, causing great hardship or loss to the individual and his/her family.
Yes this is a distinct possibility. I used to post with me real name and once had a radical LDS poster make all sorts of threats. Thus I have since become an anonymous hypocrite.
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When I left my SB church about 4 years ago, I simply walked out the door. In those 4 years, I can recall just 2 phone calls from new Deacons introducing themselves to me and letting me know their availability. When I see folks from my church in public, they are friendly and kind, and we chat up a storm as always.
If I could be prophet for a day I would give local bishops and SPs ability to remove members names without any further paper work. If person did not attend for a certain period I would contact and ask them if they wanted to receive visits and/or remain on the roles. If they did not want to be on the roles I would take their name off. It would make a bishops life much simpler.
There is no harrassment, no shunning whatsoever. None.
Some shun others don't.
I can think of no reason for, nor one single instance of an EV setting out to "screw" another because they stopped attending.
I do not think you see it over not attending as much as you do when someone turns against it.