It used to be that only presidents had a list of enemies, and if you were on it, it was kind of a badge of honor, as long as you didn’t mind having your tax returns audited.

Newsman Daniel Schorr was reading President Richard Nixon’s enemies list during a live broadcast when he came across his own name. Actor Paul Newman said he considered his inclusion one of his greatest achievements.

“If you don’t have enemies, you don’t have character,” Newman said at the time.

Now everybody can join in the fun of making enemies.

A new Facebook plug-in called EnemyGraph allows you to keep a list of your “enemies” along with a list of your “friends.” Both terms are badly abused by the social network site.

The application was developed by a researcher and two of his students at the University of Texas at Dallas, and it has many thousands of users.

The professor, Dean Terry, said they were simply looking for a way to “broaden the conversation.”

If, for example, a Facebook friend has made an enemy of your favorite band, you will receive an alert. At which point, I suppose, you either have a good laugh together or you toilet-paper his house.

Terry said the team was responding to Facebook’s open challenge to “hack the graph” by turning what he called its “enforced niceness culture” on its ear. After all, the site has long resisted cries for a “dislike” button to go along with its ubiquitous “like” button.

EnemyGraph was launched in March with its own Facebook page and its own Twitter feed, and it became what student designers Bradley Griffith and Harrison Massey called “performance art” when Sarah Palin blasted it during her appearance on the “Today” show.

If nothing else, it is fun to go to EnemyGraph.com and see what is trending among haters. It is an odd mix.

Crocs, fake tans and Farmville were trending at one point. Justin Bieber was on most enemies lists.

The trouble is, you reach the top of the trending enemies list if a bunch of people make you an enemy all at once, and that is a recipe for bullying if ever there was one.