A term used to refer to something that splits up a group of friends. Usually that something drives the group to become annoyed and angry with one another until they all go their seperate ways. That something is typically a newcomer to the group that the rest do not like. Or that newcomer could be there to specificlly split up the group for their own sick pleasure.
This term came from the woman, Yoko Ono. Who is blamed for the breakup of The Beatles. She dated John Lennon. Yoko is said to have fought often with the other band members and did not keep her distance during recording sessions. She was the factor for The Beatles breakup.
Person: "Did you see the Buffy episode about how Spike infiltrated the group and got them all not speaking to each other?
Another Person: "Yeah, that episode was called 'The Yoko Factor'"