Sometimes, as in the picture, the crap is inflatable and capable of being carried great distances by the tiniest puff from a windbag.
Some PRs do an excellent job representing their employers, promoting a cause they feel strongly about, and banging the drum for people or a problem that would otherwise get little or negative attention.
My favourite-ever interaction with a public relations expert was when I called him up and put it to him his client had been caught in fairly minor but nevertheless slightly criminal and embarrassing activity.
The spinmeister launched into a five-minute diatribe about the morality, drive, and motivation of his client, his deep understanding of the problems such behaviour would cause and that he would simply never, ever, under any circumstances, have behaved in the way I suggested.
"We've got it all on camera," I said. "Well, in that case he's very, very sorry," replied the PR man, and you could barely notice the screech of mental wheels as he reversed everything he'd just said.
Then there are those who - as with every trade - get the rest of their number a bad name by employing the one simple rule of "lie, lie, and lie again, and if you are caught out lying the best thing to do is keep on lying".
Such people fixated on twisting the truth over all other concerns can achieve short-term wins but unless their boss has the wit to get rid of them once those gains are established their continued employment eventually causes only trouble.
This type though is rare and it is far more common to find people working in PR who just haven't got a scooby how it's supposed to work. The ones who don't understand they cannot control anything much, and that their task is to influence rather than shout, panic or refuse to answer questions.
The Royals have the same problems as any other family, made a thousand times worse by lottery winner-style wealth, public expectations and constant scrutiny. When their PR machine is running well that's how we see them.
But when it gets a spanner in the works - from any cause, be it staff holidays, a miscommunication, or plain stupidity - the machine does something which makes the Royals look like inbred feudal overlords interested only in shagging, shooting and shushing everyone else.
In 1931 the king-to-be began an affair with an American divorcee. It was reported in foreign newspapers but not British ones, thanks to the Palace machine and a long-departed sense of deference. Silence got them nowhere though because in 1936 after the prince became king Bishop Blunt of Bradford denounced the relationship from his pulpit, the news exploded, and a few months later Edward VIII abdicated.
In the 1970s Prince Charles began a long affair with Lady Kanga Tryon. She went on to develop addictions to painkillers and alcohol, went to rehab, and was confined to a wheelchair after falling from a window. Charles avoided her in public despite saying she was "the only woman who ever understood me", and she died from sepsis at 49. Silence about the fling was necessary when both were married, but the story got out anyway and it hardly makes Charles look good.
Henry VIII married his second wife before he divorced his first. Queen Victoria spread gossip a female courtier was pregnant to see her hounded from court when in fact she had a liver tumour and died a virgin.
Princess Diana threw herself down the stairs at Buckingham Palace while pregnant. Princess Anne's first husband had a lovechild he refuses to publicly acknowledge. In 1909 the Royals locked one of their princes away because he developed epilepsy - a condition which can be minor or severe, but never deserves incarceration. Videos have got out showing Prince Harry describe a fellow soldier as "our little Paki friend" and infamously dressed as a Nazi for a laugh.
All those things are private. They involve medical information, personal photographs, private relationships, and stuff that happened behind closed doors. Some were known about at the time and some leaked later.
Reporting any of them today - despite the fact there are public interest arguments to have for many of them - would breach the Press Complaints Commission Editors' Code of Practice and could lead to injunctions and privacy cases under Article 8 of the Human Rights Act.
The point is that, public or private, right or wrong, we do know about all of them because the first and most important rule of PR is that the truth always comes out in the end.
The role of the PR practitioner is to ensure that, when it does become public knowledge, the reputation of their client is not damaged as a result. Anne got divorced, the latest book by Prince Charles' biographer insists Diana was bonkers, and Harry is a war hero with a ripe turn of phrase.
It's worth the expense of deploying expensive lawyers to put pressure on those who wish to discuss such things if whatever they might publish is damaging, untrue, or deeply unreasonable.
But to do it when what they might publish has already been seen around the world, makes your client look a little more human, and is already a topic of national conversation is a bit of a cock-up.
It is not only a case of bolting the stable door after the horse has already won the Grand National, it's guaranteed to make whoever ordered it to seem like an out-of-touch, over-sensitive, power-crazed and pompous pillock whose army of ten spin doctors aren't earning their money.
I wonder who it was?