People are mixing up Walmart's retail practices with their online practices.
Walmart's retail arm will squeeze water from a stone. However, their online division actually works with suppliers since they're still trying to compete with Amazon and eBay.
Yep, there's absolutely no reason they won't squeeze the online sellers later. They already have the precedence with their stores and suppliers. Shit, once they get the ball rolling with their online shop, they could even find products to kick the sellers out and negotiate with the suppliers themselves (the most likely result long term).
Walmart's retail arm will squeeze water from a stone. However, their online division actually works with suppliers since they're still trying to compete with Amazon and eBay.