While the line may not be clear, the effects can still be devastating, especially when trust is broken.
According to Boston.com, lawyer and newlywed Bostonian Feyisara Olotu had a clear definition: "If you can't do something in front of your wife, that's cheating."
As the article points out, today it's very easy to send a quick tweet to an old sweetheart, or carry on a Facebook chat with a friend of a friend, while an unsuspecting spouse sits just a room away, and often closer.
In an article featured on Livestrong.com, infidelity can cause distrust, grief, obsession and retaliation in a relationship.
However, the question bouncing around the Internet is whether it constitutes cheating if it is virtual infidelity. According to an MSNBC report, "many Americans seem to think it does."