It will be hard for future (>700 years away from now) historians to discover a lot about what we thought today: writing personal and professional letters (e.g. "letters to the editor" in learned journals, letters to an uncle living in a different city) and diaries is happening less and less compared to the last 200-300 years.

Perhaps we should go ahead and have a few hundred thousand emails printed with a special lasting ink on velum to pass it on to our successors ("Codex Electronicus"). On reflection, my own inbox is perhaps rather too nerdy - it would introduce a strong selection bias to posterity's view about us.

> is happening less and less

Do you have any evidence for this? Even assuming it’s true, doesn’t the volume of podcast/YouTube/email/facebook/HN posts more than make up for it?

The key word is letters. Physical, printed letters that a historian in the 2400s can physically hold and read.

Digital communications will decay and vanish beyond repair, leaving our current era's ephemera irrevocably lost to the ages.

http://howicode.nateeag.com/data-preservation.html