Essentially, "liking" something on facebook that you don't actually have sincere interest in.
Some do it to fit in by liking what popular people liked.
Some do it to reinforce in everyone's minds that the he/she is, indeed, friends with the poster of the status.*
Some do it to make sure
everyone knows that he/she was a part of the
inside joke in the status.*
Some do it to create the illusion that he/she was a part of the
inside joke in the status.*
*You can interchange 'status' and 'picture'.
Examples of Liking to be Liked:
One, Two, and Three alllll liked Four's status, so I did too.
Five's status was nothing special, but I liked it because I wanted to make sure
everyone knows I know her and I'm tight with her.
Six made her status about all the drinks we had, but she didn't name names, so I made sure
everyone knows I was the one she had drinks with (in case anyone is unsure I drink) by liking it.
One of Seven's statuses was about her and Eight drinking, and even though I wasn't there, I had to make sure
everyone knows I do like to drink (in case anyone doesn't know I'm hardcore) so I liked it.
