Pity the future generations of historians, who will have to make sense of the past from almost inexhaustable amount of data. Blogs, e-mails, tweets, you name it, there are lots of them. Some may be deleted and will be unavailable in a decade or two, but given there are often multiple copies of the same source stored at different locations and media, it’s unlikely that we will lose all or much of these materials.
The historians of future may well not be humans, but a computer programme that can crunch through huge number of sources and make some sense out of them. Perhaps computers will become sentient beings. Even if such (terrifying) situation does not arise, the future generations of historians may resemble more computer programmers than lone scholars immersed in the libraries and archives, inhaling mould.
As people like to say, many things written, shared and consumed on the net are mundane and utter rubbish, and they ought not be preserved for posterity. That is true, and there will always be a place for high politics and structural or sociological analyses. However, information is information, and historians can only speculate about what is missing whereas historians are very unlikely to ignore what exists. The problem is not the lack of sources, which often hampers historians today, but too much information. Ever since ordinary people matter (and we should matter) in history and history writing, historians disregard the popular at their peril.
In one respect, perhaps, the post-modernists were right: there can be no master narrative anymore. There are too many sources that can be neatly fit into a single narrative.