In September 2011, The New York Times ran an article about a small town in Missouri called Mountain Grove. Gossip and rumors have always existed in this tight-knit community, but before the days of anonymous social media sites, people traded stories at the local diner called Dee's Place. At Dee's Place you could usually find a dozen longtime residents who gathered each morning to talk about weather, politics, and, of course, their neighbors.

But of late [the article reports], more people in this hardscrabble town of 5,000 have shifted from sharing the latest news and rumors over eggs and coffee to … a social media Web site called Topix, where they write and read startlingly negative posts, all cloaked in anonymity, about one another. [Unlike sites like Facebook, which require users to give their real names, Topix users can pick different names and thus remain anonymous.]

And in Dee's Place, people are not happy. A waitress, Pheobe Best, said that the site had provoked fights and caused divorces. The diner's owner, Jim Deverell, called Topix a "cesspool of character assassination." And hearing the conversation, Shane James, the cook, wandered out of the kitchen tense with anger.

His wife, Jennifer, had been the target in a post … which described the mother of two, as among other things, "a methed-out, doped-out [addict] with AIDS" Not a word was true, Mr. and Mrs. James said, but the consequences were real enough …. Now, the couple has resolved to move. "I'll never come back to this town again," Ms. James said in an interview at the diner. "I just want to get … out of town."

The article concludes with a warning about gossip: "The same Web sites created for candid talk about local news and politics are also hubs of unsubstantiated gossip, stirring widespread resentment in communities where ties run deep … and anonymity is something of a novel concept."