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 channels specifically were experiencing this problem? It's nice to flush out fake subscribers, but I'm worried that subscriptions that aren't spam may be removed, and that you may be using this to defuse the current subscription war the platform is having.