I moaned about Tesco's self-service tills ages ago. So long ago, in fact, that my moaning predates this blog so there's no link I can give you. But basically I grew concerned, having scanned my shopping and having been forced to take a plastic bag for a handful of items, I swiped my debit card and was shocked when I was not asked for my PIN number.
Beyond the obvious initial shock at Tesco for not asking for a PIN number at a till, my attention quickly turned to Visa who were clearly authorising the payment anyway. If this is the case, surely any merchant (or possibly just some with a certain reputable status, but still) is 'allowed' to charge a Visa card without any authentication whatsoever.
This sets a certain dangerous precedent… and at the very least it allows any old thief to do snatch my card, do lots of grocery shopping, fly through the self-service tills then pay for it and run away.
Essentially, the problem totally invalidates the usefulness of the PIN readers at the standard checkouts, because anyone using a stolen card will simply opt to use the self-service tills, and then the only people asked to key in their PIN numbers will be the real people using their own credit/debit cards.