Analog shopping is inherently social. There’s the flea market stroll, the girls’ outing, and the time-honored encounter with a mall Santa. But e-commerce, a category that’s expected to reach $200 billion this year, has yet to reap full benefits of the social networking revolution. The two seem as compatible as reindeer and sleighs, yet the universe is littered with proof of awkward pratfalls. (After all, who wants to learn on Facebook that their significant other bought an engagement ring at Dave’s Diamond Barn?) That explains why Facebook killed Beacon, a function that automatically published a user’s e-commerce interactions to news feeds. Apple’s Ping, which shared iTunes buys, flopped. And Blippy, a well-funded startup that shared credit card purchases on social networks, pivoted earlier this year to do something—anything—else.