I wasn’t going to blog about this, but the surprised response of some colleagues when I mentioned it this morning told me that it was more interesting than I thought. The story: Visa opens a swap shop for designer clothing in central London – but just for a few days. The question: why?

The Visa Swap site explains the concept this way: “Clothing event to encourage sustainable fashion through ethical swapping activity”. You take your designer cast-offs and fashion experts give you a special Visa card with points on it. You redeem the points (this coming weekend) for other designer items. Anything left over on Sunday evening goes to the specialist fair trade/development charity TRAID which does this sort of thing, except for cash, all the year round. Result: well, lots of good news coverage.

It’s obviously good marketing – from the fact that I’m writing about it. It also positions a product (Visa) which is all about spending as being imaginative and having an ethical heart. The question for me is could they take it further than that? Digital currencies are easy to manage, and they don’t have to be backed by currency. Most electronic cards have the space to carry lots of parallel types of value. It’s already done one deal with World of Warcraft which could take it in this direction. There’s a boom going on in swapping stuff (see eBay) which would work even better if money didn’t have to change hands. Its conventional business, at least in the affluent countries, is already migrating from a credit business to a debit and prepaid business, as Dave Birch of Consult Hyperion pointed out recently on the Digital Money blog. So maybe – counterintuitive as it seems – the Visa Swap shop is a modest stalking horse for another business extension, but with added reputational and image benefits.

And if you want to join in – you’ve got to the end of the week to take your stuff down to Knightsbridge to get your points before the weekend excitement begins. But – to judge by a column earlier this week (skip past the bit on the 2012 Olympic logo) – there’s a lot more for girls than boys at the moment.