There’s a German word for it, of course: Sehnsucht, which translates as “addictive yearning.” This is, I think, what these sites evoke: the feeling of being addicted to longing for something; specifically being addicted to the feeling that something is missing or incomplete. The point is not the thing that is being longed for, but the feeling of longing for the thing. And that feeling is necessarily ambivalent, combining both positive and negative emotions.

A paper titled “What Is It We Are Longing For?” published in The Journal of Research in Personality, breaks down these “life longings” into essential characteristics. They target aspects of our lives that “are incomplete or imperfect”; involve “overly positive, idealized, utopian imaginations of these missing aspects”; focus on “incompleteness on the one hand and fantasies about ideal, alternative realities on the other hand”; result in a “temporarily complex experience” combining “memories of the past, reflections on the imperfect present and fantasies about an idealized future” (this is called “tritime focus”); and that “make individuals reflect on and evaluate their life, comparing the status quo with ideals or successful others.”

In other words, your average Pinterest board or inspiration Tumblr basically functions as a longing machine.

Pinterest’s sudden and spectacular rise has been met with some skepticism, and it’s often talked about in that particular dismissive way reserved for things that have the temerity to seem both frivolous and feminine. Not surprisingly, some of this loathing is internalized. Someone on Pinterest once posted a slide that read: “Pinterest: Where women go to plan imaginary weddings, dress children that don’t exist and decorate homes we can’t afford.” But to focus on the “aspirational” aspect is to miss the point. People don’t post stuff because they wish they owned it, but because they think they are it, and they long to be understood, which is different.

Pinterest didn’t create this urge to use visual evocations for little pleasure jolts; in fact, its success lies precisely in being behind the curve. The site’s co-founder, Ben Silbermann, has said that in creating the site, he was just picking up on something people were already doing — i.e., collecting beautiful things and using them as a way to express who they are to the world — and making it easier for them to do it. What the company provides is a clean, well-lighted place to collect found images and share them with others. In fact, the company discourages people from posting images they have created themselves, preferring that they venture out into the wilds of the Internet looking for beautiful things to bring back to the cave.

Silbermann suggests that collecting online is a form of self-expression for people who don’t create. “If you walk around Brooklyn and ask people how they express themselves,” he said in a speech at New York University, “everyone’s a musician or an artist or a filmmaker. But most of us aren’t that interesting. Most of us are just consumers of that. And when we collect things and when we share those collections with people, that’s how we show who we are in the world.”

Not everyone buys into this, of course. Here’s The Awl’s co-editor, Choire Sicha, for instance, on the subject of rebloggers who fancy themselves curators: “As a former actual curator, of like, actual art and whatnot, I think I’m fairly well positioned to say that you folks with your blog and your Tumblr and your whatever are not actually engaged in a practice of curation. Call it what you like: aggregating? Blogging? Choosing? Copyright infringing sometimes? But it’s not actually curation, or anything like it. . . .” To which a commenter added: “My Tumblr isn’t so much curated space as it is a symptom of deeper pathologies made manifest.”

“Curation” does imply something far more deliberate than these inspiration blogs, whose very point is to put the viewer into an aesthetic reverie unencumbered by thought or analysis. These sites are not meant (as curation is) to make us more conscious, but less so. That might be O.K., but it also means they have a lot more in common with advertising than they do with curation. After all, advertising trains us to keep our desire always at the ready, nurturing that feeling that something is missing, then redirecting it toward a tangible product. In the end, all that pent-up yearning needs a place to go, and now it has that place online. But products are no longer the point. The feeling is the point. And now we can create that feeling for ourselves, then pass it around like a photo album of the life we think we were meant to have but don’t, the people we think we should be but aren’t.