In a the Internet is both too ephemeral (self-hosted blogs disappear, Youtube videos get taken down) and too persistent at the same time; I don't think that most Twitter posts of non-public figures would need to remain public forever by default, for example, and I don't think I need to mention various data breaches.
The Internet Archive somewhat mitigates the first issue, but it makes me pretty nervous that there's essentially just one organization doing what used to be much more distributed to various physical libraries.
For the second one, I hope we'll see better solutions (both technical and social) as the technology and our interactions with it mature.