I'm not sure if it is excessively literal, though; if Facebook disappears within 10 or 30 or 50 years, presumably all of the data on Facebook will disappear with it.

Even ancient civilisations kept orders of magnitude more records than have survived now, and they even had the added bonus of being physical — with linguistics the only obstacle to future generations' reading of their content. Our mass of data that seems so permanent is wrapped up in proprietary file formats; it's stored on volatile media; and it's kept around by companies who, in the context of centuries, are flashes in the pan.

How much of the digital information you possessed even ten years ago is still readily accessible? I know in my case there's not a great deal. Now extrapolate that forward 50, 100, 150 years…