One way that Historians learn about the past is by reading the private letters that people send to each other. In particular they hunt for letters from Famous people. Generals, scientists and politicians. While scientific letters and reports or the draft of a bill may tell you what happened it'll rarily tell you why and it's the why of it that is history. Which means that Historians are going to need to better journalists and do their research while the Famous people are still alive to talk to them about it. Historians much prefer dealing with dead people. Dead people don't throw heavy objects at you and scream at you to leave them alone you damn vulture. I suppose this means we are going to see a whole new wave of Papparazzi intrusions into peoples personal lives. Only now it'll be to get solid data on what people say and think.
People kept and keep letters for many personal reasons. But I doubt the intent was ever to allow them to be made public. Letters usually get into the Historians hands when a generation inherits them that never knew the person sells them or donates them.
Basically if your in any way famous and you want your private life to remain private you have to remember to destroy your letters in a non-recoverable fashion. Mandating their destruction in your will may not be enough.
I'm a big fan of history but I tend to dislike the fact that Historians and Archeologists often intrude on the privacy of dead folks who went to alot of trouble to be left alone. Re: Tomb excavations. The answer is simple. Write the book beforethe source is dead. Make History a living dynamic thing rather than a B&E perpetuated on and desecrating the dead.
A Mummy was once a person. A person with beliefs as to how he/she was to be buried and cared for after death. A person who had religious beliefs that are profaned when someone comes along and digs him/her up and puts them on display.
But then I probably have a strange view. I believe the dead remain people even after death. That they have the right to privacy in their tombs and graves and in their personal corespondance.