To provide transparency to end users we recommend opt-in users to mailing lists based on their interests (the information on how to collect users via specific opt-in groups you can find here) and then attach these mailing lists to the corresponding email campaigns. The most relevant and recommended way – to attach one mailing list to one particular email campaign. Thus, by unsubscribing from an irrelevant or boring topic, the end-user still would be able to receive relevant newsletters based on the user's interest.
Keeping this in mind, Piano ESP moving in the direction to display mailing lists on the unsubscribe page. Previously we used to display a list of campaigns on the unsubscribe page, and there was an issue when end-user unsubscribes from the campaign but still can receive a newsletter. The reason for the case is that this mailing list is also attached to another campaign(s). For the end-user, it could be a real mess and a serious issue that is not obvious. And for Piano ESP customers this could lead to a significant decrease in loyalty.
Subscribe/unsubscribe events don't go anywhere, and you easily can find it at the 'Analytics' section → Mailing list activity page.
Please note: we stopped collecting campaign-related subscribe/unsubscribe events and have hidden the 'Campaign subscribers events' graph for the reasons described above.