I was listening to Connecticut Public Radio one recent morning, during the long process of waking up and I was very impressed -- negatively -- by what I heard.
The discussion was extremely interesting and, I think, important. But some participants kept saying "you know."
Those on the radio who were professional broadcasters typically spoke in full sentences and hardly ever used filler phrases such as "you know," "like," and so on.
Other people on the program (Wheelhouse, I believe it was) were "ya know"ing so much it made my head hurt. I am not a public speaker nor do I ever speak on radio, which is good, because I umm and hmm and uh just like everyone else.
However, I do not think I say "you know" as an all-purpose noun, preposition, semi-colon, or whatever it's being used as. I'll admit to using "like" occasionally, but I'm usually saying it for rhetorical effect, as in, "So, like, then he says, why do you have horns? And I go, you know, I'm like the devil," etc.
I am not an overzealous grammarian or a person who diagrams sentencesand I am aware that English usage does change over time.
How hard is it to change one's speech to avoid saying "you know" every fifth or sixth word? That's the question. If it were as difficult as learning Latin, then I would understand why people in the communication biz say "you know" with abandon.
Otherwise, why not train yourself to stop saying "you know" constantly? You would sound better and way less irritating, especially for people who are just waking up.