The phenomenon of internet predators that fabricate online identities and entire social circles to trick people into emotional/romantic relationships (over a long period of time).
Possible motivations: revenge, loneliness, curiosity, boredom
Hiding who you really are to hook someone into an online relationship using Facebook, Tumblr, Twitter, MySpace or by cell phone.
Guy 1: "Hey so I met this new girl online! She is so hot!"
Guy 2: "Have you ever seen her in person?"
Guy 1:"No, does that matter?"
Guy 2: "Better make sure she's not a catfish.."
Guy 1: "You think she's catfishing?!"