E-mail is , of course, cheaper and encourages quicker thought, and it introduces a peculiar blend of the personal and professional. The AIP historians have also detected a decline in the use of lab notebooks, finding that data are often stored directly into computer files. Finally, they have noted the influence of PowerPoint, which can stultify scientific discussion and make it less free-wheeling; information also tends to be dumbed down when scientists submit PowerPoint presentations in place of formal reports.
Generally, though, these new communications techniques are good for scientists, encouraging rapid communication and stripping out hierarchies. But for historians, they are a mixed blessing. It is not just that searching through a hard disk or database is less romantic than poring over a dusty box of old letters in an archive. Nor is it that the information in e-mails differs in kind from that in letters. Far more worrying is the question of whether e-mail and other electronic data will be preserved at all. —Robert P. Crease —The lost art of the letter (Physics Web)
When I write major projects, I typically save multiple drafts under different file names. But for routine work, like many people out there, I just save the new work over top of the old. I can see that denies future historians access to rough drafts.
While I doubt future historians will ever comb through my materials, the point is that historical methods will have to change to account for the fact that much of our writing is ephemeral and interactive, which means future historians will likely have to spend more time reading e-mail exchanges and tracking down obscure references to data that is no longer available, rather than reading stand-alone essays.
I recall reading that as people started doing more of their daily work via telephone, historians faced difficulty piecing together events that in a previous century would have left a paper trail. E-mail is at least more friendly to archivists than telephone conversations.