Do you see how annoying it is to read "you know" so often in the prior paragraph? No one would deliberately write that tedious repetition into a document, but many people cannot stop themselves from the verbal tic of inserting "you know" into every conversation, sometimes more than once in a single sentence. This overuse of "you know" is painful to listen to, and if those infected by this logomania were aware of how it sounds, they'd take drastic steps to cure themselves.
Oh, come on, what's the harm, you might ask? The harm is multiple. First, it makes the speaker seem unsure of him/herself, as if constantly asking for validation of what's being said (though it's unclear what the speaker means by "you know," given that it could either be a question or a statement). Second, it's obviously a bad habit, and who wants to call attention to a bad habit? Third, it makes the speaker seem inarticulate, out of control, which is never a good thing. Fourth, it annoys listeners not similarly infected—just when you think you're being clever or amusing, your interlocutor is silently cringing at what you're saying. Finally, it interferes with whatever message or thought the speaker intends to convey because it distracts from the essential communication. If what you say is worth hearing should it be dressed up with ugly, meaningless interruptions?
Suppose you yourself are infected by this speech diarrhea and want to be cured. Is there hope? A twelve-step program? Poor baby, what can you do? Ah, my friends, Dr. Douglas is here with the remedy, so calm yourself and take careful notes.
First of all learn if you can hear yourself saying "you know." That will be difficult because you're used to your own cadence, but, as with all bad habits, being aware of the difficulty is a major step forward. If you're able to spot your "you know"s, you'll be embarrassed by how often you utter these inanities. However, if you can't hear your own overuse, or think it's minor, try another step. Get a friend (I'd be glad to volunteer) to say "I know" to you as an interrupting reply every time you say "you know." That will be shocking to you at first, then as annoying to you as the overuse of "you know" is to others, and, finally, so embarrassing that if this experiment is repeated daily for four days you'll build in an automatic dread of "you know" being followed by "I know," and the disease will be in remission.
Adopt this rule: the only time you should say "you know" is when you actually expect the other person to indicate understanding of what you've said.
Facebook has a site called "Society Against Major Overuse of 'You Know'," dealing with what it calls a "crisis sweeping our globe." I'm not sure "crisis" is the right word, but the overuse is damned annoying.
"Picking Your Battles: The Meaning of Words," July 3, 2011