Many people are interested who has unsubscribed from their channel. When you compare two gathered lists of your subscribers (an older one and a new one) then you can see who isn't in the list anymore. Tube Toolbox could sort out these users and show them. Would be really nice and could be interesting/helpful. I think its not so hard to realize, comparing 2 txt files is still possible (Editor/Word)
AdminTube Toolbox (Admin, Tube Toolbox) commented
Same answer as above:
Here's the problem: YouTube will only allow you to view the first 1,000 people who subscribed to you. So, assuming you have more than 1,000 subscribers, there is NO WAY to be sure if someone is subscribed to you or not. That fact makes this feature impossible.
People (including us) have requested that YouTube allow us to view more than 1,000 subscribers and I have a feeling like someday they will allow it. As soon as they allow it, I PROMISE we will add this feature immediately.
If you all want to help, please visit the following link and tell YouTube that you want the feature added!