There's an old newspaper adage, known as 'Greener's Law', that states: 'Never argue with someone who buys ink by the barrel.'
William I. Greener Jr, who served as White House deputy press secretary during the Ford administration, borrowed this warning not to take on newspapers or their columnists, from Mark Twain; so by September 1978, when it was quoted in the Wall Street journal, the old aphorism was already rather old.
Now, as we bask in the dawn half-light of the brave new world of digital media, Greener's Law looks ancient, and there's an obvious reason for that: media power ain't what it used to be.
So, if the power no longer lies so completely in the grasp of those who purchase paper by the ton and ink by the vat, what's the modern equivalent?
*Never argue with someone who has over a million uniques a month, maybe?
*Never argue with someone who has more than 200,000 Twitter followers?
And one for journalists:
*Never argue with someone in the comment section of an article you've written?
The shift in power, as represented in the modern media marketplace, is a subtle one, and one illustrated by the above hastily cobbled together digital Greener's law.
Those sites that get a million uniques in the cut and thrust of modern news media are likely to be part of the same strata of society that Greener warned against challenging.
The Twitter followers rule could apply to the new moneyed elite - the closeted world of celebrity, but also to those who would have traditionally rubbished their enemies in the pages of titles they own or write for.
It is, therefore, only the rule about arguing with those that comment on an article you've written that illustrates the shift.
Journalists in the digital age, in common with celebrities, newspaper editors and owners, have the power to reach a huge audience with their views.
Like celebrities and newspaper editors and owners, it is, of course, part of the reason you get into the game in the first place: 'all writing is dead language, until it finds a willing reader', etc.
It's perhaps unsurprising therefore that the shift in power causes some journalists so much discomfort.
The shift is away from being able to - with impunity - spout what the heck we like in the knowledge that if someone doesn't like it, or thinks its wrong, all they can do is write an angry green ink letter and pop it in the post.
Similarly it's also not surprising that celebrities dislike the shift in power that technology like Twitter, for instance, has brought about - a shift that allows a previously silent band of folk, who think whatever the precious star is feted for - they didn't ought to be, to tell them just that.
The digital shift means that those who broadcast, write and disseminate their views, products and services to the masses now have to answer for them.
And this is surely where trolls, and their more fearsome associates, the haters, are rather useful - they puncture the self-importance bubble of those who have the tremendous privilege of a platform, and they remind them that not everyone thinks they're bloody marvellous.
Trolls, of course, get a hard time these days - for being offensive, for being racist, for bullying - and in lots of cases it's impossible to justify what they do, apart from saying - to use to the words of a colleague: 'As long as there have been people, there have been dickheads.'
But trolls, like the trolled, ain't what they used to be either. The misuse of the world troll to describe anyone who is unpleasant to anyone else online is a dangerous foil for a different kind of argument, one that would seek to restore the safe power structure of old. It means all negativity and disagreement can be easily and swiftly undermined with the use of just one word.
This is a particular danger as at some point we appear to have forgotten quite what an amazing thing this new digital interaction is. The good of digital engagement, seen in the firestorm of chatter, in the millions of interactions that take place, on social media, on comment forums, on websites like this one, is now such a given good that we only ever seem to talk as though the opposite were the case.
For journalists this represents a particular opportunity, the ability to view immediate feedback on what you're doing, and how you're doing it. The ability to see within minutes whether what you're writing is having an impact, and what kind of impact it's having.
Opinion formers who have a privileged platform should, therefore, take a more relaxed and open-minded view about what goes on below the line.
There are, no doubt, vast swathes of bullshit that drift around comment sections, but there's also a lot of gold, humour and - if you don't take offence - plenty to learn about who you're writing for.
That the internet is made of people is something its too easy to forget. And sometimes, when you read below the line it's actually hard to believe. But there is value in a lot of the interactions - even if that value is merely the reminder that the people who pay your wages are no longer as quiet as they used to be.
The moral panic over trolling, and the dangers of some kinds of web-based interaction has soured sensible discussion over how useful some parts of the new way of doing things can be.
Part of the reason why some of those with a platform don't realise the value of this kind of interaction is that the depiction of the open internet is one of a worrying, troublesome wild west of a place, populated by people hell-bent on doing you harm.
Little by little the value placed on digital engagement between those traditional centres of powers, including reporters, and their readers, is being undermined.
Perhaps the answer is for those who have a platform to recognise what a privileged position that is to be in, and to start to engage with the wilder sections of the marketplace of ideas. And perhaps we'd all benefit from a reminder of just how impressive this new process is.
The trouble with asking people what they think, is that they might actually tell us. The trouble - and the opportunity, that is.