Amazon, Kelkoo, Moneysupermarket, lastminute. Price comparison websites have transformed the way we shop - saving consumers millions and earning millions more for visionary entrepreneurs and the investors who backed them. So when a new price comparison site for the grocery market launched this week, it was bound to attract big media attention.

Mysupermarket.co.uk promises to save shoppers 20% on their weekly shop, on average, a claim that prompted founder and director Johnny Stern to declare the site, last week, as the eBay of online grocery shopping. This week he was revising that claim. "We want to be the next Google," he told us, when we roadtested the site (see p31). "We want to give the shopper one site to serve all their needs for supermarket shopping."

This is heady stuff. But which is it to be? Both eBay and Google are stupendously successful, but they have hugely different business models. And, frankly, neither of them resembles that of mysupermarket anyway. Indeed, it's difficult to see where the new site will generate its profits. There are no revenue-sharing agreements in place with any of the stores whose prices it monitors (a central plank for both Google and eBay); there's no advertising on the site (Google); and in the space of a week, it's quietly shelved a plan to charge user fees (a strategy that neither Google nor eBay nor any price comparison website has pursued).

And all of this comes before we even begin to consider the cost of monitoring and comparing 20,000 supermarket items. Or the functionality of the website, which as our roadtest showed, was shaky. Don't get me wrong. I share the view of this week's Retail Industry Forum that online shopping will increase. But I'm sorry. mysupermarket ain't the way.