I have little time for politeness. Now don't get me wrong, I like civility, which is how civilised people treat each other, how people treat each other in a proper civilisation. And I'm a big fan of civilisation, which is why I live where I do, and not in the British Empire. But politeness has little to do with civilisation. Politeness is a shopkeeper's idea of civilisation, civilisation as imagined by a good Protestant. It has the form and motions of civilisation, without the culture, without the soul; it's practised most of all by charlatans and pretenders to civilisation, who don't have any genuine belief in the concept.
What's the difference between politeness and civility? Within whatever norms are accepted by a culture, civility is showing others that you have consideration for them. Politeness, on the other hand, is telling others that you have consideration for them. It's not enough for the polite individual merely to act in a civil manner; he must also accompany it by visual and verbal cues, so that a whole audience can acknowledge his refinement. In fact, as long as the form of politeness is observed, it's rarely considered necessary to back it up with actions; once Ps and Qs have been carefully tended, the polite individual can quite happily insert a dagger.
I'm always wary of polite people, partly because when I'm being polite myself, I'm usually being insincere. I tend to fall back on the forms of politeness when I can't genuinely bring myself to act in a considerate manner: I'm generally only polite to people I dislike, or don't care for. If you feel the need to signal your consideration far and wide, I suspect it's because you can't be confident the consideration is really there.
I'm convinced a lot of politeness is pure humbug. For some, it's a hypocritical reflex, and for others, it's motivated by a terror of offending anyone, lest they be offended themselves. Indeed, one strand of politeness could be defined as the terror of making anyone feel anything at all, the terror of inducing emotion in another human being. In some cultures and subcultures, it's considered impolite to make any direct statement, to express an unambiguous opinion about anything. There are some Usenet guardians who would replace every occurrence of the phrase "this movie sucks" with "IMHO I think I dislike this movie, but that's just my opinion, YMMV, etc." Under their rule, the information content of every discussion would approach zero, but at least there would be milky-tea harmony all round, and no one would be threatened by the dangerously liberating power of an honest thought.
And so I think it's a sign of decline when politeness is considered to be the same thing as civility, as I feel it already is in some places. To change anything, to improve anything, impoliteness is almost necessary; you'll have to offend someone. But increasingly, politeness is applied as a blanket to all public discourse; people are so obsessed with the forms of politeness that they can no longer tell when the form is inappropriate. I still wince when I remember the Democrats who politely allowed Bush and co. to steal the 2000 election: one instance when to act in a truly civil manner would have required the abandoning of politeness wholesale.