Amazon.com may be the king of online retail but the king of offline retail, Wal-Mart, may have Amazon.com’s throne on its mind. Yesterday, Walmart.com added one million new items to its catalog thanks to the launch of the Walmart Marketplace.

What is the Walmart Marketplace? As the name suggests, it’s the Walmart equivalent of the Amazon Marketplace, a program that enables third party merchants to hawk their wares on Amazon.com.

The “select group of retailers” participating in the Walmart Marketplace includes CSN Stores, eBags and Pro Team. Walmart says that the retailers it’s working with were chosen “based on their strong
customer service track records and large assortments of quality brands and
products
” and that it plans to continue adding retailers going forward.

ChannelAdvisor CEO Scot Wingo posted a great review of Walmart Marketplace on his blog which highlights some of the similarities and differences between the Walmart Marketplace and Amazon Marketplace. Perhaps the biggest difference: the former “is much more ‘closed’“. That’s not entirely surprising given Walmart’s exacting standards for suppliers; and quality over quantity it could turn out to be a key differentiator if Walmart sees it as one.

So should Amazon.com be worried? It’s probably a bit early for that. But the world of online retail is evolving and many of the advantages Amazon.com alone had in the past are being eliminated as offline retailers get more sophisticated and comfortable with the internet.

The one advantage Amazon.com does still retain: its name is synonymous with shopping online. Far more online consumers head to Amazon.com than head to Walmart.com. As Scot Wingo points out, Internet Retailer pegged Walmart.com’s 2008 sales at $1.7bn compared to Amazon.com’s $20bn. But by taking pages out of Amazon.com’s playbook, Walmart.com and others might just be able to close the gap.

Photo credit: oswaldo via Flickr.