I agree @Jeruba. With letters though, and I am sure you have found this yourself, I have been able to go back through the archives and find letters from people who I’m sure when they wrote them would never have thought they would be of interest to anyone. They were just going about their daily business but because there is a hard copy letter, they end up filed in a box or a filing cabinet and hoarded thankfully so we can look at them now. In the case of the work I am dealing with now, the Lieutenant-Governor of the State I am interested in was obsessed with record keeping so there are lots of things available. Plus a whole series of handwritten journals from another important source.
In contrast, in our recent State election tweets/Facebook posts made by politicians in the lead up to the election were taken down almost immediately some of them were not elected/lost their seats. That info is gone. Yet in the future, people wondering how we communicated democratically in the 2000s will want to see those posts/comments. Historically, we could dig through letters, letters-to-the-editor, journals and the like. Even if the writer destroys his copy of the letter, the carbon copy or the receiver may remain out there somewhere. If something is erased from the electronic record, those posts/comments won’t be there. People can so easily destroy them.
A biography of one of our former Prime Ministers has just been published and some of the research relates to letters/notes written by the Governor-General and relating to a major part of our political history. That someone kept the notes and letters from other parties allows us now to look back retrospectively and say “we didn’t know that person was involved at all”. So fascinating.
I hope you are right and much of this content is kept – somehow – I am not confident though and it will be a huge loss to future historians. Sorry if I derailed your thread @zensky. It is such an interesting question though… what will people in the future want to find in our packages.