On Facebook, when one person's comment is liked by another person, whose responding comment is then liked by the original commenter.
Can be used for many reasons, the most common being:
2. Eagerness to appear as though one has a private joke with someone else
3. Desire to publicly proclaim the good standing of a relationship to the world (whether true or false).
Vanessa: Wow, I can't believe Brit-brit and Jen-jen are so self-absorbed that they keep parallel liking everything!
Angie: Yeah, especially since they had that big fight yesterday...everyone knows they don't really get along anymore.