Can I be notified each time someone unsubscribes?

Yes, you can be notified by email each time someone unsubscribes.

To do so, enter your email address on the page Subscribers → Edit settings (for the relevant list) → General. You will then automatically receive a short message in your mailbox each time someone unsubscribes.

You can view all subscribers that unsubscribed under the tab unsubscribed (above the table with subscribers on the page Subscribers → View).