AS of this morning, there are 7.2 billion people on the planet.

If you believe every claim, 1.19 billion of them are on Facebook. That's either an awful lot of people wedded to the champion of social media, or an indication of the vastly greater number who can't be bothered or manage without.

Who doesn't use YouTube? Those handy with industry "analytics" say 6.2 billion have yet to see a YouTube pop video or a hilarious clip of a cat upended. What about Flickr, Instagram, Pinterest? They claimed, respectively, 87 million, 150 million and 70 million devotees last year. Half a billion people use iTunes; 300 million employ Skype. Ubiquity eludes these media.

The best example is probably Twitter, until the year's end a stock-market sensation, despite never having achieved a profit. Some of its users behave as though all the world is attempting to communicate in messages no longer than 140 characters. The truth can be expressed as pithily: Twitter has a very long way to go before all those grandiose evangelical claims of an interconnected humanity come close to being a reality. As of October 2013, the service had 500 million users - but only 215 million of those were "active".

Once I swore I would never have anything to do with Twitter. The number of people capable of saying anything of interest in 140 characters struck me as vanishingly small (it is). The number who could resist self-promotion, nastiness, or pursuing politics without using the typographic equivalent of A SHRIEK didn't seem impressive (it isn't). The attractions appeared limited.

Tweeting publicly, you can soon find yourself reminded that the number of people you would cross a street to avoid hasn't diminished since last you checked. When Caroline Criado-Perez was subjected to anonymous threats of rape and death last summer for campaigning to have Jane Austen's image on a banknote, the case against Twitter was pretty convincing. Why volunteer to introduce yourself to scum?

You could make a case. You could say, first, that by avoiding the ugliness and the risks you let thugs win. You could say that the contest over free speech matters. You could argue, above all, that disdain for change is not going to halt change.

I gave in to Twitter for less elevated reasons: the herd was thundering through. In journalism and politics in Scotland in 2014, a year with some significance, Twitter amounts to an important, if ramshackle, forum. In terms of discourse, it is more like the badlands of the Wild West than Periclean Athens, but as a responsive, collective medium Twitter is as staggeringly fast as it is flawed.

Witnessing the Clutha tragedy as it unfolded was a case in point. That night, journalists and others all over Glasgow and Scotland mounted an impromptu rolling news operation through Twitter that was wondrous to behold. No important fact reached traditional outlets that had not already been sourced and tweeted. A great deal of rubbish and rumour went through the mill, as ever, but the self-organising nature of the thing meant that nonsense was soon weeded out. The story was gathered and told as though by an ideal virtual newsroom.

Twitter is fascinating, meanwhile, if you have any interest in the forms of the written word. A lot of the better tweets are shaped like a classic gag, with set-up and pay-off. A lot of the very worst, even by "educated" types, simply prove a truism: some people really can't string two sentences together. As for the character limit, I feel an odd nostalgia. If you ever had to write headlines within the unbreakable rules of hot-metal type, when fonts could not by tweaked with clever software, tweeting isn't so hard.

But Twitter, like most of the social media, like most forms of digitised communication, attracts all sorts even as it excludes billions. The numbers who think a pinnacle of technological achievement is just a grand excuse for vile and sneaky abuse is staggering - social media bring the witless and the worst flocking, much as dank, cosy shadows attract cockroaches.

And there is an unpalatable fact: clever technology doesn't make the stupid any less stupid. In fact, there are numerous claims that fast, frictionless social media are making things worse - witness the claim from 2008 that attention spans shortened from 12 minutes to five minutes in the space of a decade.

Is that claim true, however? It might be explained by an impeccable theory (mine): tales of social media reducing attention spans can probably be explained by people failing to pay attention. The 2008 study of 1004 people was conducted on behalf of Lloyds TSB Insurance, an outfit with a certain interest in lack of concentration and domestic accidents. Hard science? That's not beyond dispute.

Similarly, the furore started when Nicholas Carr wrote a 2008 article for Atlantic magazine entitled Is Google Making Us Stupid? did not subside with his subsequent book, The Shallows: What The Internet Is Doing To Our Brains. Suddenly there was a lot of talk of "brain plasticity", the loss of the ability to contemplate, of the evaporation of real thinking in an accelerated, overloaded world. Again, however, the scientific evidence was thin. It is too early to tell.

But then, what does anyone need to know? Twitter is utterly facile - how could it be otherwise? If all you know is what Google passes off as the only truth, what can you ever know? If information is grazed and attention flits like a butterfly, knowledge is a glittering shadow.

According to work by the Pew Research Center, fully 73% of Americans now avail themselves of social media. This is impending reality. So the species adapts, bit by bit, tweeting its sense of unease.

@IanBell1916