The nature of ‘like’ has been a topic of much recent linguistic study. Part of its appeal is that it’s a part of English that has been undergoing rapid and fairly drastic change, and to linguists, that’s damn exciting. Language change is what drives linguistic diversity, what makes Russian incomprehensible to the Portuguese and Beowulf unreadable to speakers of modern English.
The ‘like’ we’re talking about here is considered polysemous: it has more than one role in English. There’s the old-fashioned comparative like, which even your grandmother will use: You look just like your great aunt Mildred did when she was your age! Then there’s the newer focus marker like, which is used to draw attention in on a key aspect of a sentence: The dog was like, drooling all over me. Often the focuser like will imply hyperbole, in a way that can be seen as an extension of the older comparative meaning. For example, in the sentence Amy weighs like, twenty tons, the speaker does not mean that Amy actually weighs twenty tons, but, you know, it’s kind of like she does.
Finally, there is the like that is under investigation here: what linguists call quotative like. It’s used to introduce reported speech: So she’s like, “That totally sucked. ” It’s a similar phenomenon to quotative ‘go’: And then I go, “No way, dude, it’s a cheeseburger! ” The word all can be either added to or used in place of quotative like: I’m all like, “We need to go now.”; She’s all, “We can’t park here.”
Quotative like can be a nifty linguistic device. It’s more generic than reply or exclaim and more casual than even say. It can be used not just to introduce actual speech, but also gestures or your own internal monologue: The whole time we were talking, I was like, “Oh god, get me out of here!” It often implies shades of imitation, introducing reported speech that mimics the original speaker in tone and tempo, and in that sense is closely related to the comparative like. It’s typically an indicator of a lighthearted tone of speech, something youthful and flippant-sounding.
But is it a deponent? I’m doubtful. All of these functions evolved from the comparative like, which is not the same thing as the verb ‘to like,’ meaning ‘to be fond of.’ The comparative like is a preposition, and has no tenses. Instead, to form a complete sentence, it must be used with a verb: you can run like the wind or pose like a model. If it’s not a matter of doing anything, but just being similar to something, the construction be + like is used. There’s a crucial difference between this and the verb to like: compare I am like my father to I like my father, for instance. And in this same vein, I was like my father is not a passive version of I liked my father; it’s an entirely different thing, in which like serves as a meaningful particle connecting the verb to a noun phrase. Quotative like is the daughter of comparative like, what happens when its function and meaning expands, and as such is not a verb but a preposition. It combines the verb (‘be’) with its object complement (the quoted phrase).