Personally I'm in the camp that I want history to be lost. That's part of the appeal to me. In fact my favorite feature in the fedi is Mastodon's option to enable auto-deleting posts of a certain age.
Only content that is explicitly pinned or reaches a certain amount of interactions should be saved imo. Since that's the stuff you'd actually want to preserve rather than the 99% of forgettable content, and it would also drastically cut down on file hosting.
Another thing is that a federation should only act as the exchange between users on ActivityPub. It should only cache relevant information and not be expected to store everything, like I wrote before. The user should be a portable account that is stored on a device. The federation server would sync your account between your devices, but not store it. You send your content to the federation, and then the federation sends it out into the world where they choose to do what they want with it. The federation shouldn't hoard it indefinitely.
Also this makes sense from a privacy perspective. If you care about privacy, why would you also want all your data indefinitely stored? Unless certain things are relevant and explicitly kept, it should be expected to expire and be lost by default. Where did we get this expectation that data should be stored forever? Also you expect it to be stored forever and not be trained on by AI?
This comment for example, after about a week or two most of the visibility and interaction of it will drop to zero. At that point, this comment should expire and no longer exist. I wrote this comment, it reached some people, and served it's purpose and should expire. I'm not going to pretend like this comment is some kind of historic document that should be indefinitely preserved, nor do I expect or want it to be.
