In love’s newest incarnation, students might spend their evenings Skyping and messaging deep into the night with someone they met online who lives five states away. Eventually they drift off to sleep with their laptops open only to wake up hours later, dazed and bleary-eyed, whereupon they tap their screens back to life and say a warm hello to their e-lover in another time zone.

UNLIKE hookups, these relationships are all about sharing your every thought, idea and emotional burp. But they are also, crucially, about being able to close your laptop and turn off your phone whenever you want to and continue about your life as you wish, unencumbered.

When a couple involved in an online-only relationship finally decides to meet in person, their experience often mirrors what happens in “Her” when Theodore tries to have sex with his OS via a human surrogate, but then backs out when the experience feels too weird. Same with real couples. After all that cyberintimacy, being together physically simply doesn’t feel right. The body doesn’t match the sensibility. It’s too hard to square the person to whom they’ve been baring their heart with the one who’s suddenly sitting next to them. Such encounters crash and burn with surprising frequency. But if the couple felt as if they had gotten to know each other so well online, how could that intimacy suddenly drain away?

One explanation: They didn’t actually get to know each other so well. They only got to know what was served up, a two-dimensional collection of images, text and, for some, audio. When the messy parts of us aren’t on display from the beginning of a relationship — when awkwardness and fumbling and being forced to be present without a mouse-click escape hatch all enter the scene — it’s hard to catch up. As good as it felt to be able to create an ideal version of ourselves, it can feel jarringly worse to have that control suddenly yanked away.

Which leads to a second explanation for the high failure rate: For many, the urge to seek pleasure through a device rather than through a person who’s in the same room can be a hard habit to break. In this wondrous world of the Internet, we often find the object that’s far away to be more enticing than the one that’s nearby.

One woman I heard from had been reveling in a monthslong online relationship with a man who lived hundreds of miles away, and their bond had grown so intense that they finally decided they had to meet and see if their online magic could translate into an actual relationship. So one Friday she rented a car and drove nine hours to spend a long weekend with him. And it went O.K. at first. But soon it became clear that their online chemistry wasn’t happening in real life. Their once urgent conversations had dribbled away to nothing. Now that they were physically together, it was as if they each had become the person to escape from instead of the one to yearn for.

Before long he began sneaking glances at his cellphone when they were at a restaurant and drifting away from her to his open laptop when they were back at his apartment. Until eventually, in a perfect tableau of their relationship’s demise, she was left to sit quietly aside as he searched online for the emotional fix he’d grown accustomed to finding there, scrolling for something, anything, to capture his attention.