It seems like every MBA in the US has done at least one case on WalMart, and you end up learning about its tremendous buyer power, unique (and recently changed) market positioning, how its competitive strategy/advantage evolved, and mostly about its ridiculously efficient supply chain.
I wandered about recognizing some these patterns that I'd learned about, when for some reason I ended up striking a conversation with an elderly lady who seemed to be working in the greeting card section of the store. It turns out she didn't work for WalMart at all, but for Hallmark.
She was just a Hallmark vendor who stocked card in the two aisles at WalMart, and her compensation was based directly on what and how much customers ended up buying, hence she had to be really careful about what she stocked and how she stocked it. According to her this WalMart actually had a bunch of these vendor-controlled aisles (But she said, "they aren't exactly keen for you to know that".) It makes you appreciate what a complex eco-system retail can be.
Her take on it: "Its a great job for me to have as a semi-retired person. Y'know, a little additional income, I get out of the house and meet some people and things don't fall apart if I miss a day.."