Alike (past tense: aliked) is a verb that means to click a Facebook like button. This is true of any Facebook or other web page with a Facebook like button on it.
For example, if you clicked the like button on Justin Bieber’s Facebook fan page, you aliked it. If people saw you do it there’s a pretty good chance that they looked at you as if you were an idiot, but that has nothing to do with the definition of alike.
The word alike was coined to make it easy to conversationally differentiate between actually liking something and merely clicking the related Facebook like button. For example, you might try to save face quickly by saying, “No, no, no. I didn’t actually like Justin Bieber. I merely aliked him.”
Following from the literal definition of alike, many people use the word metaphorically to refer to any instance when someone mindlessly asserts meaningless approval of anything, regardless of the medium they used to assert it.