A small book with an essay of Harry Frankfurt from 1986 - newly published in 2005, where he analyses what bullshit means, how it is dissimilar from bluffing and lies. It comes to the point only in the later part of the essay, and for me the statement of bullshit is:
It is impossible for someone to lie unless he thinks he knows the truth. Producing bullshit requires no such conviction. A person who lies is thereby responding to the truth, and he is to that extent respectful of it. When an honest man speaks, he says only what he believes to be true; and for the liar, it is correspondingly indispensable that he considers his statements to be false. For the bullshitter, however, all these bets are off: he is neither on the side of the true nor on the side of the false. His eye is not on the facts at all, as the eyes of the honest man and of the liar are, except insofar as they may be pertinent to his interest in getting away with what he says. He does not care whether the things he says describe reality correctly. He just picks them out, or makes them up, to suit his purpose.
Both in lying and in telling the truth people are guided by their beliefs concerning the way things are. These guide them as they endeavor either to describe the world correctly or to describe it deceitfully. For this reason, telling lies does not tend to unfir a person for telling the truth in the same way that bullshitting tends to. Through excessive indulgence in the latter activity, which involves making assertions without paying attention to anything except what it suits one to say, a person's normal habit of attending to the ways things are may become attenuated or lost. ...
[The bullshitter] does not reject the authority of the truth, as the liar does, and oppose himself to it. He pays no attention to it at all. By virtue of this, bullshit is a greater enemy of the truth than lies are.
Why is there so much bullshit these days? Frankfurt states that if one has to speak about something, about which one does not know anything, only bullshit can result. This fits e.g. to politicians, but also resonates with the feeling that a responsible person in today's democracies has to be informed about everything - which is in reality impossible ... so more bullshit results.
He raises the question why we are so tolerant against bullshit (compare it to our reaction against lying!), but leaves that 'as an exercise to the reader' unfortunately, and also has no answer to that in the video interview with Harry Frankfurt about the book
He also states that the amount of bullshit has lead to a kind of skepticism that we can know how things truly are. Therefore many of us retreat from the ideal of correctness to the ideal of sincerity, so staying true to ourselves. But Frankfurt argues that this is not possible without any grounding in an objective reality either, which leads to "sincerity itself is bullshit".
Cited is also In The Elder Days Of Art.
BTW, there does not seem to be a good translation of the word bullshit into german, so the german edition of the book also uses bullshit.