Computer science researchers at the University of Colorado Denver report a study in which 40 percent of participants said they would avoid further personal contact with someone who unfriended them on the social networking site.
"People think social networks are just for fun," study author Christopher Sibona said. "But in fact what you do on those sites can have real world consequences."
Sibona said he studied factors that predicted whether someone would avoid a person who unfriended him or her.
"The number one predictor was whether the person who said the relationship was over talked about it to someone else," Sibona said. "Talking to someone is a public declaration that the friendship is over."
Traditional face-to-face communication is giving way to more remote online interactions with their own rules, language and etiquette, he said.
"The cost of maintaining online relationships is really low, and in the real world, the costs are higher," Sibona said. "In the real world, you have to talk to people, go see them to maintain face-to-face relationships. That's not the case in online relationships."
In the real world when a friendship ends it usually just fades away, he said, while on Facebook it can be abruptly terminated by one party declaring the friendship over.
"Since it's done online there is an air of unreality to it but in fact there are real life consequences," he said. "We are still trying to come to grips as a society on how to handle elements of social media."