The stress comes, Marder theorizes, from the kind of personal versioning that is so common in analog life -- the fact that you (probably) behave slightly differently when you're with your mom than you do when you're with your boss, or with your boyfriend, or with your dentist. And it comes, even more specifically, from the social nuance of that versioning behavior colliding with the blunt social platform that is The Facebook. Behaviors like swearing and drinking and smoking, the study suggests, are behaviors that you (might) do with friends -- but not (probably) with your boss. And, more subtly, language that you might use with your friends -- in-jokes, slang, references to Breaking Bad -- probably won't track when you're in a different social context. The awareness of that discrepancy -- Facebook's tendency to disseminate even highly targeted social interactions -- leads to stress.

This is not a small concern. Per a recent Pew study, some 80 percent of parents who use social media have friended their children on Facebook, and half have -- eesh! -- posted messages on their kids' profiles. And, in the professional sphere, a CareerBuilder survey found that 37 percent of hiring managers use social networking sites to research job applicants, with 65 percent of that group using Facebook as their primary resource.

Which is another way of saying that Facebook is George Costanza's worst nightmare: It enforces, second by second, the collision of worlds. The Edinburgh study found that only one third of Facebook users took advantage of its listing privacy setting, which can be used to control the information seen by different types of friends. It also found that, on average, people are Facebook friends with seven different social circles. The most common group was friends who were known from offline environments (97 percent added them as friends online), followed by extended family (81 percent), siblings (80 percent), friends of friends (69 percent), and colleagues (65 percent). Those are, in the sociological sense, very different groups -- groups that carry different (and unspoken-because-obvious) behavioral expectations. And yet there they are on Facebook, jumbled and tangled and stewed -- brought together by a single platform, and navigated with a single user identity.

Facebook's power, and its curse, is this holistic treatment of personhood. All the careful tailoring we do to ourselves (and to our selves) -- to be, say, professional in one context and whimsical in the other -- dissolves in the simmering singularity of the Facebook timeline. The circumstantially mediated relationships typical of IRL interactions -- you see your boss at work, your friend after work, your mother-in-law at Thanksgiving -- are mediated instead by one overarching, and overpowering, circumstance: Facebook. Suddenly, Work You is the same as Family You is the same as Friend You (is the same as Gym You is the same as Cooking Class You is the same as Trip to Thailand You is the same as Road Trip You is the same as Words With Friends You is the same as Happy Hour You). The You itself -- which is to say, you yourself -- gets flattened, condensed, homogenized. Contextual personhood gives way to comprehensive personhood. You become, for better or for worse, universal.

Which: stressful! Because, as liberating as it is to erase the divides that separate formerly fractured identities -- as nice in theory and in practice as it is to live an all-purpose, one-size-fits-all existence -- the mingling comes with costs. Social expectations from the IRL realm haven't quite caught up to Facebook's assumptions (some might call them "impositions") about how social lives are lived. Facebook wants us to -- and, really, forces us to -- conduct our digital lives with singular identities: identities that can be harnessed and streamlined (and sold to and analyzed). We, however -- we as people, we as cultures, we as societies -- tend to expect that identities will be what they have been since the advent of society itself: prismatic. Varied. Contextual. These tensions will inevitably clash. They will come to terms with each other as Facebook adapts to users' expectations and, more to the point, as users adapt to Facebook's. In the meantime, though, users are bearing the brunt of the conflict. And that is, yes, stressful.