Some retailers have (reportedly) stopped accepting Visa Debit cards (and presumably Debit Mastercard too) because the fees make it an undesirable prospect for a retailer to accept such things. I wasn't aware that the fees were so different between credit and debit cards, but it makes sense for retailers to refuse them in that case. They don't have to pay high fees to financial institutions just to make their customers happy, but it's kind of in their best interests. What's in Visa and Mastercard's best interests, however, is to make the style of card a non-issue to retailers, mostly because their advertising and whole concept for these cards is to use your own money where credit is usually the only option. If big retailers stop accepting them, then slogans like "Accepted everywhere Visa is" have to be dropped, and suddenly the appeal to consumers is lost too.
Mokalus of Borg
PS - It's a good idea that just needs a little work.
PPS - Woolworths, contrary to some reports, still accepts these cards.