I'll be on radio tomorrow talking about the rise of vaping.
ASH (the vapers' friend) published the results of its annual survey into the use of e-cigarettes and vapourisers last week.
This year's headline stat was the fact that, for the first time, more than half of UK vapers 'have given up smoking' (BBC News).
According to ASH:
In 2012, there were 700,000 vapers in the UK, now there are 2.9 million.
Some 1.5 million vapers are ex-smokers, compared with 1.3 million who still use tobacco.
The rest are mostly dual users. Only a tiny handful of vapers have never smoked.
More pertinent perhaps is the fact that the rate at which smokers are switching to e-cigarettes has peaked.
Some people, including ASH, seem to think a major reason more smokers aren't switching concerns the perception of harm:
A growing proportion of the public and smokers fail to recognise that e-cigarettes are less harmful than smoking.
That may be a factor. Personally I think there are other reasons why (to quote ASH CEO Deborah Arnott) "The rapid growth in e-cigarette use has come to an end."
First and foremost, the rate at which smokers were taking up vaping was unsustainable.
E-cigarettes appeal largely to those who want to quit smoking or those who want an alternative nicotine device in places where smoking is prohibited (dual users).
Sooner or later that market was going to be saturated because the number of smokers who want to stop isn't as great as tobacco control would have us believe.
In fact a significant number of confirmed smokers (95% according to one recent study) enjoy smoking and don't want to quit.
A small majority accept they are addicted but it doesn't seem to bother them because the enjoyment outweighs other considerations, including the health risks.
Although the majority of vapers are now ex-smokers, a substantial number are still dual users who vape only when they're not permitted to smoke.
As vaping is increasingly banned where smoking is prohibited there is less incentive to switch (which is why the likes of the Royal Society for Public Health want smoking banned outside pubs as well).
Several generations on, e-cigarettes are not yet capable of giving the majority of smokers the experience they crave. For a variety of reasons many don't enjoy vaping.
Some of this information can be found in The Pleasure of Smoking: The Views of Confirmed Smokers which is based on a study of 600 smokers by the Centre for Substance Use Research.
But I'd like to suggest two more reasons why the rate of smokers switching to e-cigarettes is not what it was.
One, the more anti-smoking groups like ASH try to 'own' e-cigarettes as a smoking cessation tool the less attractive they will appear to the many smokers who loathe and detest the quit smoking industry.
And who can blame them? Tobacco control's latest proposals - a ban on smoking in social housing and a ban on smoking outside pubs - tells you everything you need to know about these despicable, puritanical bullies.
Two, if you read ASH's Smokefree GB survey in full (the name alone indicates the direction of travel) you'll stumble upon something quite interesting.
When asked what would prompt them to try an e-cigarette again, only 5% of smokers said, 'If I were recommended a specific product by someone I trusted.'
An even smaller number (1%) said, 'If I knew other people who used them.'
So when harm reduction campaigners talk about enlisting an "army" of vapers to go out into the world to spread the message, like a latter day temperance movement, I'm pretty certain they're barking up the wrong tree.
In fact I suspect that far from welcoming their evangelical advances millions of smokers - even those who want to quit - will react the same way most people respond when door-to-door preachers come knocking, with a polite but firm, "Thanks, but no thanks."
The same is true, I believe, of stop smoking services that try to 'educate' smokers to switch.
There's a reason stop smoking services are haemorrhaging clients - the number of smokers may be in long-term decline but so is the number of smokers who wish to quit.
The two are inextricably linked and there must come a point - very soon - when local government has to pull the plug on a service that few smokers want or need.
After all, if smokers do want to quit the overwhelming majority has always done so without state intervention - most recently by voluntarily switching to e-cigarettes, for example.
Which brings me to another point. Many advocates of vaping are so deeply engaged with the anti-smoking industry it's difficult to tell them apart sometimes.
Far from resisting tobacco control and excessive regulations some are effectively collaborators, happy to throw smokers under the bus if it helps their cause.
They deny it but their silence on anti-smoking legislation, including smoking bans, plain packaging and so on, speaks volumes.
It's indisputable too that many supporters of vaping are tobacco control activists whose anti-smoking agenda is well known and over-rides, I think, the harm reduction argument.
In terms of tobacco they are prohibitionists, pure and simple (albeit creeping prohibition). So can you blame smokers if they view their promotion of e-cigarettes with suspicion and mistrust?
Having been stigmatised and denormalised for years by tobacco control, why would you take advice from people who support more and more regulations to achieve their Utopian goal of a 'smokefree' (sic) world?
And why would you listen to those who, by virtue of their silence, are effectively collaborating in your denormalisation?
The simple fact is, the rapid growth of vaping, like the rapid decline in smoking which reached its peak between the mid Seventies and early Nineties, took place when there were relatively few regulations.
Education and increasing understanding of the potential health risks of smoking led to fewer people doing it.
It didn't need a tsunami of repressive laws or an army of anti-smoking evangelists to convince millions to stop. They made an informed decision to quit (or not start) all by themselves, just as it should be.
Smokers must also be allowed to decide for themselves whether to cut down or quit by switching to e-cigarettes. Millions have already done so; some are now ex-smoking vapers and others have decided to continue smoking. If that's their choice good luck them.
What they don't need is unsolicited lectures, well-meaning or otherwise, on the pleasures of e-cigarettes. If smokers genuinely want to quit and are curious about vaping they'll make that discovery for themselves.
More counter-productive still would be outdoor smoking bans designed to force smokers to switch. Even the most cursory understanding of human nature can predict how that will end.
In short, one of the biggest threats to vaping, beyond excessive regulation, is an unholy alliance between tobacco control and advocates of vaping that enlists vapers as foot soldiers and deploys e-cigarettes as weapons in the war on tobacco.
Nothing, in my view, will damage vaping more than the perception that, far from being a recreational product in its own right, e-cigarettes are merely a quit smoking tool, 'owned' and regulated by the public health industry as part of a long-term plan to outlaw smoking and, ultimately, any use of nicotine.