This may seem ironic, but having a common enemy brings people together; in fact, a common enemy is one of the key ways people align in unity (think 9/11).

So while it’s true that people bond over shared passion (hence the success of the Facebook ‘Like’), people also tend to bond over a shared enemy. To the chagrin of many, there’s no Facebook ‘Dislike’ button, so a group of developers came up with the next best thing: EnemyGraph, an app that encourages Facebook users to list the things, places, and people they dislike. Once listed, the app shares the content with like-minded ‘Dislikers,’ as a means for the dislikers to connect.

It’s a twist on how typical social networks connect people, normally based on affinities. The app’s most-mentioned “enemies” are familiar targets: Crocs, Justin Bieber, Internet Explorer and FarmVille.

What’s most interesting about the app is its encouragement of conversation amongst people who both like and dislike a common interest. For example, if you dislike something yet your friend likes it, EnemyGraph will send you a “dissonance report” pointing out the difference and offering it up for conversation.

“When I saw the first friends list at the beginning of the social media era the first thing I thought was, “where’s the enemies list?” No one ever made one, so we did.”

EnemyGraph can be installed as an app or as a plug-in through Facebook. You can download EnemyGraph here.

(Editor’s note: the EnemyGraph site has been down at times this week due to all the press coverage; they report than 10,000 users this week, with new servers on the way).