The fact of having old flames on one's friend list, however, is unrelated to commitment level, according to the report that examined whether conduct on Facebook is something romantic partners should worry about.
"People are using Facebook and other social media sites to make romantic connections with people they would entertain having a relationship with, even if they are in a committed romantic relationship," said Michelle Drouin, lead author of the paper and a psychologist at Indiana University-Purdue University Fort Wayne.
Past research indicates that Facebook has been cited in as many as one third of divorces in recent years, according to Drouin and her colleagues.
To assess the social networking site's potential role in relationship issues, the team recruited college students for their study. All of the 109 women and 39 men were undergraduates and had Facebook accounts.
The researchers looked at how many Facebook friends each participant had and asked them to rate on a scale of one to six how likely they were to initiate or accept a "friend" request from someone they considered a potential romantic interest.
They also measured participants' level of Facebook-related jealousy with a 27-item survey assessing how jealous the respondent would be if his or her partner added a new friend of the opposite sex on Facebook.
Finally, a questionnaire was used to evaluate participants' commitment to their current relationship, by having them rate statements such as, "I am committed to maintaining my relationship with my partner" and "I want our relationship to last for a very long time."
Drouin and her team found that only connections with potential romantic partners made while in the relationship - and not before getting together with one's current mate - were linked to a lower level of commitment to the relationship.
That is, participants who were less committed to their partners were likelier to accept and even initiate Facebook friend requests with people they viewed as romantic interests, the team reports in the journal Computers in Human Behavior.
But the presence of old flames that remained on one's friend list even after entering a new relationship was unrelated to the students' level of commitment to their current partner, as was how often one "friended" potential mates when single.
Amy Muise, a postdoctoral fellow in psychology at the University of Toronto, Mississauga, who was not involved in the study, offered two possible interpretations of those results.
"If someone you're attracted to or you have feelings for reaches out to you, that might lead you to reevaluate your relationship," Muise told Reuters Health.
"But more likely, you are already less committed, and so you are more interested in alternatives" to your current partner, she said.
The authors acknowledge that their findings among college students may not apply to older adults who generally use the social networking site less. They also plan to extend their research to see how Facebook interactions relate to real-world emotional or physical infidelities.
The field of Facebook research is relatively new, Drouin noted, so future studies will be needed to learn more about this and other questions regarding how social media affect human relationships.
"Facebook is a reason why some people are breaking up, and why others are getting divorced. A lot more research in the future will be directed at social networking," she told Reuters Health.
In the age of Facebook, a partner's online presence - and the way a relationship is represented online - has become a topic that mates should negotiate early on, researchers said.
"It's about having a conversation, like about other things in the relationship, about what each person's expectations are," Muise said.
Potential topics for discussion include if and how each partner wants the relationship recorded on Facebook, and what the protocol should be if friended by another potential mate.
"The challenging part is when people disagree on that," Muise said.
The best approach for the virtual world, Drouin said, is to be honest about what each partner feels is appropriate - just like in the real world.
"Have an open line of communication with your partner," Drouin said. "Be honest with each other about what you see as the perils of Facebook, and make sure you're aware of the potential risks."
Of course, the only surefire way to avoid the potential pitfalls of Facebook and other social media sites is to stay away from social networking entirely, she said.