YouTube is removing interactions
YouTube started to delete Views, Likes and Subscribers. It was announced on June 2014, but the 'real cleaning' started on September 2015. By the 'real cleaning' we refer to developed automated system for removing Views and Likes from your Video or Subscribers from your Channel.
YouTube removes inactive accounts
Their claim is that only closed or fake accounts will be affected, but that is only partial true, because, also inactive accounts will be deleted from your Subscribers. We agree that closed account, deleted account, account no longer in use and fake accounts should be deleted. But what are those inactive accounts? YouTube, similar to Facebook Policy, uses its algorithm which puts an expiration date on Subscribers, so those who do not repeatedly visits your Channel will be deleted.
According to YouTube, this will result in less spam, and number of subscribers will be more true to number of people genuinely interested in your Channel and actively watching your videos. This may be true, but they are skipping a very large group of reasons to subscribe, besides daily activity. Maybe you subscribed for one or two videos only, or to send someone URL of Channel, or to watch later and then you forget about it, or you just like to trade Subscriptions. All this, and more, can result in removing you from someone's Channel, or someone from your Channel. Also, there was a problem with joining YouTube and Google+ accounts, where after merging, all of your Subscribers and all Subscribed Channels vanished from the list. It seems that this bug had been fixed, but you still can find proof of this error if you google it. So, the message is next