In the store I work at part-time they worked out that one customer had 7 different My Waitrose cards with slight variations of his name. 6 of them were then cancelled. Plenty of people, though, will come in and buy a doughnut and then get the free coffee.
As somebody who works for Waitrose on a very part-time basis, 5% if not a lot is even less.
And it has been a biggish story on the day it is announced for years. It's a major retail operator with a multi-billion £ turnover, and I think it's seen as something of an indicator of the state of...