I did a purge a few months ago. I posted a journal first and said any of my watchers who wanted me to keep watching should comment. Some of them did. Basically, I wanted to keep watching the ones who were paying attention.
I have watched enough people since my comment above that I again struggle with notifications. I sold watches to at least 100 users and I need to think of a way to figure out who those users are so I do not break the deal.