What interests me here is the distinction between lies and BS. With lies, you are against the truth. With BS, you just don't care.
So it has a different purpose... or may not!
You may be giving BS not to convince others of your words, but to convince them of something else: say, you give 'em a lot of crap detail about issue X, not because you care what they think of issue X, but to convince them you're smart. You may want to distract them from something else (like why you haven't done something you promised). You may want to make sharp, clear questions seem fuzzy, so you can get away with something. Or not face something.
On tests, you may simply be hoping some of your guesses happen to be right. So you make lots of them.
It reminds me of the poetry of T. S. Eliot. He's not talking about mermaids and peaches and Michelangelo; he's talking about feeling old and insecure... but it works.
Those are my random thoughts on BS. What's yours? Do you BS others -- or yourself? Is your BS detector online -- and do you find others' to work too? (Feel free to BS, but be warned: with a thread title like this, everybody's going to be on the lookout for it!)
I never read the essay that made this a topic, so I won't talk about that. But I can tell you that this suggestion that big speeches are for self-promotion reminds me of what may have been the hallmark of the classical sophists. That, I suppose, would be the high end of the range. In that case, as far as I understand, there is a kind of skepticism of society--there being no knowledge of the human things, or the political things, there can be no truth. (This could be argued in this way: The science of nature studies the unchanging things--there is knowledge there; science of the very variable human things is impossible; theoretical physics is the most important, or nearly, politics the least, or nearly.) That is why persuasion is important--human beings can be dangerous, or useful--whereas truth simply does not matter.
There is a lot of this nowadays as well; I suppose that whenever there is no persuasive argument that human things do admit of scientific or philosophic inquiry, this opinion may flourish, so to speak, that there is no truth, only opinions.--I think Americans call this spin. I think it goes very far. I remember hearing Mr. Stewart & Mr. Colbert say, as a kind of defense of their shows, that they do comedy, or entertain. (Suggesting that nobody takes them seriously--they are innocent, for their activity is innocuous, & they have no influence on serious life.) But of course their comedy includes criticism of political opinions they dislike; if it is only entertainment, that is because there is no truth about the human things, or political things--all they can do is persuade those who laugh at their jokes to vote their sense of humor, so to speak...