It is insinuating itself all over the place; you can barely go anywhere without it being heard. I confess I use it. Teenage girls use it so extensively these days one wonders if they can say anything else. It is the Pervasive Syllable: "like". It's, like, totally everywhere.
I'm not a linguist, but I actually think this transformation of language, the slow creep of 'like', makes a great deal of sense, because I think it parallels, and, indeed, results from (or is it a contributing cause of, or both?) the spread of a particular style of thinking.
While it gets annoying very quickly, if you think about it, most of the creeping uses of the word make great sense. Consider the following uses, which have steadily become more common:
1. 'like' as a replacement for 'as it were' - it operates on exactly the same principles (it qualifies figures of speech), but gets rid of the subjunctive (this is my least favorite use, in part because I like the subjunctive; would that the subjunctive were more common!).
2. 'like' as an indication of approximative re-enactment: "She was like, wearing this red dress, so I was like, You're so totally not going to wear that today, and she was like, Oh, yes I am, and I was like, Well, OK, loser, and she was like, Well, I don't have anything else, and I was like, thinking, What a loser, the whole time and I, like, said she should wear green instead of red, and she was like, Like you know anything, and I was like, I do too know, and she was like, Whatever, and I was like, so mad that I, like, hit her." I'm not at all quite sure how to describe this story, so I've made up the phrase "approximative re-enactment" - it's approximative because all such uses of 'like' are approximative in that it would often be improper to think of the description as an exact description. It's not impossible that it conveys some information exactly, but the use of 'like' functions to set off some information as a unit that might be exact recall of words or deeds, but which could also just be an expressive representation. For instance, if someone says, "And I was, like, Whatever," this may mean either that he said whatever, or that he didn't, but his emotional response would have been expressed well by saying, "Whatever". The reason I call it re-enactment should, I think, be fairly clear; it is a description of events that proceeds by actually dividing up what happened into 'scenes' and representing those scenes by verbal snippets that either were said or that could have been said.
It's the impressionistic analogue to classical story-telling.
I have a hypothesis for why thinking and speaking in these impressionistic associations is becoming so common. This re-enactment function of language has a long history; but it seems to me to be encouraged by pop media, which are constructed on analogous principles. Thus, I've previously argued that movies are not plot-driven; they have plots, in the sense that they have organizations of scenes according to some idea, but the plots subserve the spectacle of the scenes, which is the primary focus of the medium. Likewise with TV. Likewise, in a different sensory modality, with popular music. Likewise many novels. Stories are presented to us almost entirely by means of representative fragments; so, when people tell stories, the easiest way they can find to tell the story is by an ordered set of representative fragments. 'Like' is a representative-fragment-indicator; it says: This unit is a distinct representative fragment in the story. Using it means you don't have to make clear in some more roundabout way that you are symbolically re-enacting the story in some way; it signals to the other person that they should fill in the story with scenes appropriate to the verbal fragment. You can see how this new use of 'like' would be connected with the way someone would talk if they were giving information for a re-enactment (e.g., a witness at the scene describing what was going on): I was like this, and she was like that. So that's my thought about it.
Of course, I could be completely wrong; but it seems to me significant that the fragmentation of stories is so common - and that 'like' is one of the ways we do this. And it is easy - it simplifies storytelling to an astonishing degree. It also comes with a number of disadvantages; but it does work for its purpose.