Classic like: I support, agree with, or otherwise am in concurrence with what you just said.
Marginal like: I pretty much support, agree with, or otherwise am in concurrence with what you just said, but I don’t feel like hashing out the finer points.
Lazy like: I pretty much support, agree with, or otherwise am in concurrence with what you just said, but I didn’t read your entire post. Or much of it at all.
Back-handed like: I “liked” your post because you said your life is stagnant drivel, or that you are pretty much a failure as a living, breathing organism.
Mindless like: I have no idea what you actually posted, but it got a bunch of likes already, so I’m going to like it too.
Obligatory like: I have no idea what you actually posted, but I haven’t liked any of your posts lately, and I don’t want you to hate me.
Reciprocal like: I have no idea what you actually posted, but you liked my last post, so I’m returning the favor.
Ulterior motive like: I have no idea what you actually posted, but your profile pic is cute and I want you to message me.
Most recent post like: I just logged on and there you were.
Guilt like: I haven’t “liked” anyone’s posts in months.
Belated like: Yes, I realize this thread has been dormant for three and a half weeks now. I had stuff to do, ya know?
Every third post like: Ignore, ignore, like, ignore, ignore, like, etc.
Inadvertent like: Whoops! I meant to click the “comment” link.