Take a look at the Valentine notices in the classified section of today's Post and you may observe an interesting pattern of behaviour.

And I'm not referring to the declarations along the lines of how Cuddles adores Poppet Pie or how Wombat can't live without Wonky One.

The annual Valentine's adverts professing undying love from people with strange pet names are invariably accompanied by some that reveal how Poppet Pie or Wonky One has brought so much happiness to the person who has paid to publicly display their affections or has made their world complete.

In other words, it's not just about Poppet Pie's beauty or Wonky One's amazing physique. It's about how they make their partner feel about themselves.

A fictional example of what happens when this is missing in a relationship can be seen on TV following the return of Mad Men, the series about advertising men in New York's Madison Avenue in the 1960s.

Betty Draper, the wife of high-powered advertising executive Don, seems to be the perfect corporate wife with her Grace Kelly blonde beauty. Yet she knows that she isn't enough for her husband. Somehow, she isn't giving him what he wants.

For, as a glance through the Valentine's Day classified adverts reveals, a successful relationship does not just depend on two individuals, but also on how they make each other feel.

And in the same way, it is becoming clear that simply producing a product and slapping a price tag on it in these credit crunched times is no longer enough.

The way that an item is regarded by the people who it's aimed at is becoming more important than ever before. Or as someone might observe in the Mad Men boardroom: "It's not the product – it's the market."

Only the other day, I realised that a lovely little shop in Bristol that sold the most beautiful vintage clothing and accessories had closed down.

The products were faultless in themselves, so I can only assume that there may have been another problem, possibly relating to how the market – or, in this case, the shoppers – felt about the products in terms of their style or price.

Another example of the relevance of the market to the success or failure of a product can be found down the M4 in Swindon, where car manufacturer Honda has suspended production for four months in response to a dramatic slump in sales.

Hopefully, the plant will be able to reopen in June. But I fear that may not be the case.

For although the cars have not changed, the demands of customers have.

It's not just that the credit crunch means people don't have as much money to spend and are reluctant to commit themselves to any long-term expenditure, such as a loan for a new car.

There is also a sense that cars are going to be altered quite dramatically in the next few years in response to declining oil supplies, with hybrid cars that combine petrol and electric engines and battery-powered vehicles becoming more functional and affordable.

And in the meantime, driving a new car suddenly doesn't feel like such an achievement anymore if the piece of shiny metal in question happens to be costing you a small fortune to run and looking rather Nineties as well.

Suddenly, sales of all sorts of products are slumping as people start questioning what they are getting out of things that they would buy almost automatically in the days before the credit crunch.

After years of producing what they wanted, all sorts of producers and manufacturers are having to look hard at how the market is responding to their products and examining whether what they are making needs to be changed to give the market what it wants.

Every industry is having to question what it's doing. The old orthodoxies no longer apply, and instead new ways are having to be found to engage with customers and build a better relationship with them.

For those companies that get it right, there is the prospect of gaining customers who are as passionate about their products as anyone so smitten that they place a soppy notice on the classified page on Valentine's day.

Get it wrong, however, and they risk suffering what every would-be suitor dreads – getting dumped in favour of a rival who does know how to make someone's world complete.

Or at least manages to sell them a product they want at the right price.