I was thinking about this as well, I think it has to do with Wal-Marts supply chain, distribution centers, and relationships with it's suppliers. I don't know the answer, but does Wal-Mart have more pull then Amazon?

Also, regarding the article, Jet from my memory gave Wal-Mart the infrastructure for online sales, so it's not like they didn't get anything for it. If anything, they are likely playing accounting games and writing off the acquisition, thereby improving their return on investment metrics into the future. When you acquire a company, there is sometimes a penalty to ROI if you pay too much, shows up in the form of intangible assets. When you write off an asset, you are basically removing it from your balance sheet.