SINGAPORE – "Be careful what you post on Facebook,” US President Barack Obama warned American high school students this past September. "Whatever you do, it will be pulled up again later somewhere in your life.”

In fact, we all are coming to learn that lesson the hard way: digital information almost never goes away, even if we wish that it would. The result is the permanency of the past in the present. This fact is one of the biggest challenges that society will face as computers and the Internet become more a part of everyday life.

For millennia, remembering information was costly and time-consuming, and to forget was a natural part of being human. In the digital age, the opposite is true: cheap computer storage, powerful processors, and ubiquitous Internet access have made remembering the norm.

Consider this: we tend to retain our rough drafts, years of e-mail traffic, and thousands of ghastly digital snapshots on our hard drives, not because we have decided that they are worth remembering, but because keeping them is now the default way of doing things.

By contrast, deciding what to delete is costly. It actually requires much more time and effort to shed data than to keep it. So we click "save” just in case.

But it is worth remembering that there is a lot of value in forgetting. Forgetting permits us to transcend details and generalize, to see the forest and not just the trees.
As some information lapses over time, the world becomes more comprehensible because we become free to focus on what is important.

Forgetting also enables us to forgive others. Fading memories of past experiences allow new memories to bloom, much as decaying leaves allow for new growth.

Forgetting thus affords us a second chance, individually and as a society, to rise above our past mistakes and misdeeds, to accept that humans change over time.

But, with digital memory, that natural process is halted. Instead, the past is always present, ready to be called up with a few clicks on a keyboard or mobile phone.

Indeed, we are increasingly confronted with outdated information taken out of context, from anachronistic news stories to emotional e-mails and compromising pictures that we had long ago forgotten.

For example, more and more employers are researching job applicants through Google and social-networking Web sites. There are already many cases of people being denied jobs or promotions because of what is unearthed. But these are reflections of a person’s past; they rarely provide accurate information about the present.

Obama’s admonishment reminds us to be more discriminating about what information we share online. His advice is essentially to practice a form of digital abstinence. It is an understandable, pragmatic suggestion – but not necessarily a good one.

We have much to gain individually and as a society from sharing information with each other. Too much self-censoring of what we do online would deny us the benefits of the Internet.

A better approach would be to ensure that digital information, like its offline variants of yesteryear, can disappear over time. First, we could give digital files "expiration dates,” so that our digital systems would delete the file when the appropriate time comes.

Second, we could opt to expose our information to a form of digital "rusting,” so that it slowly erodes (and we would need to take proactive steps should we ever wish to recover some of it).

Third, we could separate past information, so that it takes a special effort or additional time to retrieve it, thereby reducing the chances that we accidentally stumble upon it.

The more we steam headlong into the future, the more we amalgamate the data and detritus of the past and place it irrevocably into the present.

Yet it is not just how information is stored and retrieved that needs to change, but how we think about information as well. The onus is on us as much as it is on the computer.

Viktor Mayer-Schönberger, Director of the Information & Innovation Policy Research Center at the National University of Singapore, is the author of Delete: The Virtue of Forgetting in the Digital Age.