Historians are normally to be found leafing through dusty books, searching forgotten library archives or buried in archaeological digs, but this may not be the case for much longer. Reams of historical documents have already been digitised, but what about our generation's "born-digital" e-mails, e-books, word-processed documents, spreadsheets and databases that will only ever exist electronically? Researching ancestors could soon be more about tracing tweets than birth or death certificates. So, is the preservation of personal information as much a matter of historical record as it is of privacy? Digital data storage for both local and international archaeological excavation records is already commonplace, so much so that the data centres are fast becoming the new "sites" for archaeological excavation. "There are countless examples of archaeological excavations being re-evaluated through reviewing and restructuring of site archive material," says Quentin Drew, senior lecturer in archaeology at University of Wales Trinity Saint David, and an expert in digital archiving. The argument goes that digitising historical papers encourages research and at the same time keeps the original documents untouched. "In the past, scholars would have sometimes had to travel long distances to access original copies at the holding library," says Nicholas Berg, head of strategic marketing at Cengage Learning, which digitises libraries' special collections. "By digitising these materials we are allowing scholars to explore these collections through sophisticated search and browse technology." Even the physical data centre itself - the keeper of "the cloud" - has an important role to play in world history. "As archaeologists it's not just the content of those data centres that will be important to us. It's also the centres themselves - the technology, the environment in which they're housed and the physical infrastructure," says Kate Devlin, who has written extensively on digital archiving and lectures at the department of computing at Goldsmiths University of London. "Today's data centres could tell us as much about our culture as the information they contain." However, such data centres - built to house petabytes of data and internet traffic - can't expand forever. "The reality is that we are currently creating this data at unprecedented rates," says Devlin, who insists that technology isn't moving as fast as we think; we must be selective about what data is kept in the long term. "It's hard to know what will be useful to future generations but there's something delightful about catching a glimpse of the mundanity of everyday life in the past," she says. "It's a powerful thing to be able to relate in that way to someone who has lived hundreds or thousands of years before you." "What seems ephemeral to us now may seem hugely important to future generations of researchers," says Seth Cayley, publisher of media history at Gale, part of Cengage Learning. "As part of our Nineteenth Century Collections Online project we have digitised large numbers of items that were considered ephemeral by Victorians, including payslips to actors, children's adventure books and other such material." These items provide a huge insight into how people lived, what interested them and what mattered in their daily lives - though this wouldn't have been apparent to archivists at the time. Future historians might thank us for saving our spam, but could that provide a pretext for governments and private companies to store our private data for nefarious reasons? "The issue of archiving such material raises many concerns beyond just storage - not least in terms of civil liberties and legalities," says Drew. "The question needs to be clear on who would be preserving the data and for what reasons." General rules of copyright will (probably) always apply, but the ownership of data is likely to become a bigger issue in future - as will security and data protection. "More insidiously, our own willingness to share content about ourselves online means we stand to lose control over the information that defines us," says Devlin. For some data, it's too late. Matthew Stibbe, CEO at TurbineHQ.com and a trained historian, laments the loss of any digital trace of his computer games company, which in the 1990s made Azrael's Tear . "All the source code for our games has disappeared along with all the e-mail and a lot of the design documentation," says Stibbe. "All those files were on hard disks in the office and they simply disappeared." All that's left of the business is an empty box in the Computer History Museum in Silicon Valley. "In 500 years the 1980s onwards may seem like a dark age simply because all the records and physical imprint of our current generation will have disappeared in a puff of digital smoke. It'll be the greatest act of collective amnesia in human history." While we shouldn't second-guess and, in doing so, set limitations on what ancestors will want to know about us, society does need to decide on the value we place on historical research. Whether our e-mails and digital footprints are saved for posterity is out of our hands, but next time you take a great photo or think of something particularly witty that future generations will love, perhaps you should post it on Facebook. Someone's bound to archive that.