If loyalty cards are such a great idea, why isn't everyone doing them?

The most simple conclusion is, certain retailers do not believe it would give them a good enough competitive advantage to pay for such a scheme. Hugh Birkitt, chief executive of the Marketing Society, believes it is possible to have a successful business without a loyalty scheme. "It all depends on how well differentiated you are," he says. "Waitrose has a very clear position with its high-quality food."

What about Wal-Mart? Is it interested?

Although Wal-Mart remains unconvinced about loyalty schemes it is understood to have set up a research and customer insight competency last year within its marketing department in order to better understand its customers. However, this has not been replicated within Asda. "Every company researches its customers in different ways, through focus groups, surveys and questionnaires, but we do not combine this with till roll data," says an Asda spokeswoman.

And Morrisons?

It doesn't look likely. "We're not in the arena of loyalty [cards]," says Morrisons. Brian Sinclair, managing director of Loyalty Management UK, which operates Nectar, says: "For our friends at Morrisons it would be a big step to get a card out."

Is cost a big stumbling block?

It is very expensive. Asda and Somerfield have experimented with schemes in the past that have not been deemed sufficiently successful. "It would be hard to see either of them now commit to a fully fledged loyalty programme again," says Birkitt.