In 2006, psychotherapist Andrew Feldmar drove from his Vancouver home to pick up a friend flying in to Seattle. At the United States border, which Feldmar had crossed scores of times, a guard decided to do an Internet search on him. The query returned an article Feldmar had written for an academic journal five years earlier, in which he revealed that he’d taken LSD in the 1960s. The guard held Feldmar for four hours, fingerprinted him, and asked him to sign a statement that he had taken drugs almost 40 years earlier. He was barred from entry into the U.S.

Aboujaoude relates the story of “Rob,” a nurse in a public hospital emergency room chronically short on staff. His willingness to fill in when the ER needed extra hands led to significant overtime pay. When a website published an “exposé” of seemingly overpaid public employees, Rob’s name and salary were posted as an example. He was then hounded by hate mail—both paper and electronic. People called his house, and his daughter was harassed at school. Eventually the stress and constant criticism made him feel as if he were becoming paranoid and led him to Aboujaoude as a therapy patient.

The ability to forget past events, Mayer-Schönberger says, or at least to let them recede in our minds, is critical for decision making. Psychologists often note that our ability to forget is a valuable safety valve. As we naturally forget things over time, we can move on and make future choices without difficult or embarrassing episodes clouding our outlook. But when our decisions are tangled up in the perfect memory of the Internet—when we must factor in the effect of our online footprint before every new step—"we may lose a fundamental human capacity: to live and act firmly in the present,“ he says.

The result can be demoralizing and even paranoia-inducing. Lacking the power to control what, when, and with whom we share, Mayer-Schönberger explains, our sense of self may be diminished, leading to self-doubt internally and self-censorship externally, as we begin to fixate on what others will think about every potentially public action and thought, now and in the future.

Under normal circumstances, the passage of time allows us to shape our narrative, cutting out or minimizing less important (or more embarrassing) details to form a more positive impression. When we can’t put the past behind us, it can affect our behavior and intrude on our judgment. Instead of making decisions fully in the present, we make them while weighed down by every detail of our past.

The effects are not trivial. A range of people, from a long-reformed criminal seeking a fresh slate to a sober former college party girl in the job market, can find that the omnipresence of public records and posted photos permanently holds them back. At its worst, these weights can inhibit one’s desire to change. If we can never erase the record of one mistake we made long ago, if we’re convinced it will only continue to hinder our progress, what motivation do we have to become anyone different from the person who made that mistake? For that matter, why bother moving beyond conflicts with others if the sources of those disputes remain current online? With easily accessible digital reminders, bygones cannot be bygones.