David Prosser: Tesco's customers prove too clever

Outlook It must annoy new Tesco boss Philip Clarke that one of his first acts since succeeding Sir Terry Leahy has had to be reining back a generous price guarantee scheme after a small group of customers spotted a loophole and began to exploit it to make a few quid.

Still, Tesco's Price Check mishap is a timely reminder to businesses that in an internet age, consumers are more collective – and savvy – than ever before. As credit card lenders discovered when thousands of borrowers used their generous interest-free special offers to take them to the cleaners, if you're going to launch a high-profile consumer promotion these days, you had better be sure it is loophole-free.