Heads up, Creators: On Dec 13-14 you may see a noticeable decrease in your sub count as we remove spam subscriptions. If spam is removed, you'll see a YouTube Studio alert: https://goo.gl/qGDBvX This should help give you confidence that the subs you do have are real fans!
What exactly are your criteria for "spam subscriptions"? How do I know you won't unsubscribe me from a channel I still occasionally want to watch? How will I know if you do?