As the story goes, a man hungry for a snack went down the street to the 24-hour grocery. When he got there, the manager was locking up. The would-be shopper said, "Hey, the sign says you're open 24 hours." And the manager replied, "Yes, but not in a row."”

So if you always suspected that the drivers of engagement and loyalty for grocery shopping involved Convenience, Range of Merchandise, Value-for-Dollar, and Free Delivery, you’re going to love this news: is starting a new service as an online grocer.

After testing the service – called “Amazon Tote” in Seattle, named for the reusable, weatherproof tote bags your order gets delivered in – the online-bookstore cum retailing website is in the process of creating a free, no-minimum-purchase-necessary, weekly, you-specify-the-day, home delivery service. Right – just like the on-line grocery purveyor Fresh Direct, but not as convenient. Not yet anyway.

Clearly, the service is designed to encourage customers to use Amazon as their main retail destination for regular household purchases as well as, well, everything else. Likely it hopes to strengthen its position as a challenger to Wal-Mart, which is currently the largest retailer in the United States—and is reported to be developing an on-line strategy for groceries and household goods, expanding its same-day, in-store collection service.

Keeping up with consumer expectations is always a challenge, driven exactly by brands reaching beyond satisfaction to delight, and changing the category as they do so. Having watched Amazon become, well, Amazonian in other categories, this is one story where consumers may write a totally new ending.