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!
I'm honestly glad this happened because I did sub4sub like a year or two ago and I've been wanting the inactive subs from it gone. I don't know why everyone is getting mad about this.