And since the top of the thread is getting a lot of eyes, I'll reiterate the above, that 100% capture and preservation is not what librarians and archivists have all been wanting when they've made these observations.
Ephemerality can be good! Some things should come and go.
But the idea that things are online so they're stable and permanent and LESS volatile than a book has been... a real bane for a lot of us.