Surely the most flint-hearted Scrooge must have been saddened to contemplate the cheerless Christmas that seems to await customers of Farepak.

The Christmas savings company went into administration last month, taking hundreds of thousands of customers’ money with it.

These poor, vulnerable and financially illiterate people have been sending money to Farepak all year to pay for a hamper full of goodies or shop vouchers, but the prospect of much cash being returned seems slim. (A fund into which supermarkets and banks are contributing may provide some consolations.)

But customers who put money into schemes such as Farepak’s don’t need a bankruptcy before they’re losing out on the deal. It can be much cheaper to simply head down to the supermarket and buy the sort of products you would find in a Christmas hamper. Even the most transparent schemes, run by the supermarkets themselves, sell vouchers throughout the year that are redeemable only in the holiday season. Some will add a small bonus. Any financial expert in the land will tell you that you would be better saving in a proper high-interest account than using any Christmas saving scheme, both because you will earn a better return and because you will have the flexibility to spend the money how you like.

That is true, but rather misses the point. Flexibility is exactly what the customers of Christmas savings schemes do not want. Instead, they will have struggled for months to pay off the credit-card bill from last year and sworn to themselves that this year, they will save in advance and not be tempted to blow the cash on a summer holiday or a few good nights out. Christmas savings schemes are the modern-day equivalent of Ulysses tying himself to the mast.

From the perspective of rational economic man, or a personal-finance guru, this behaviour makes no sense. But to a growing band - behavioural economists such as David Laibson and Richard Thaler - it is all too familiar. We vow to give up smoking, pass on the third beer or to save more. Then temptation comes along and we light up, drink up and pay for it all on a credit card.

For many people, some kind of Christmas savings scheme seems to make sense. The relevant comparison is not between a high-interest savings account and a no-interest Christmas scheme; it is between a no-interest Christmas scheme and paying for Christmas with the help of a loan shark.

The mere existence of Christmas savings clubs is discomfiting for economists of every stripe. For the traditional mainstream, they are simply unwelcome evidence of irrational behaviour. For the behavioural economists, they pose a different problem: they are exactly the sort of commitment strategy that sensible people would resort to, knowing that they will not resist temptation without help. Fine. But some people are still getting a terrible deal. It is not easy to go beyond the behavioural insights to work out what policy should actually be.

Richard Thaler and his colleague Cass Sunstein have been blowing the trumpet for what they call “libertarian paternalism”, the manipulation of opt-ins and opt-outs to encourage people to do what they really want to do without ever compelling them.

A nice example is Thaler’s successful scheme “Save More Tomorrow”, where corporate employees pre-commit that some portion of future pay rises will go into their pensions. But “Save More Tomorrow” could equally have been the slogan of a Farepak agent. “Libertarian paternalism” is persuasive in principle. The challenge will be to get it right in practice.