All true. I've also heard other dirty stories about Walmart. One example is below along with my own latest problem with Wmart (where I shop constantly).
They order a large number of items from a private business, in this case it was a greenhouse. They do this with a contract, greenhouse produces X items at Y price for Wmart. Greenhouse goes nuts, yay, lots of business, a guaranteed buyer. Next, Wmart says "We want to keep buying from you, but we can only do it at a volume of 20X." Greenhouse says sure, expands (with loans), another year's contract. Woot woot. Process may go on another year. Eventually, Wmart says "Now we want 300X, but we are only paying Y/3." Greenhouse is in debt up to their eyeballs, has previously been making mad money, spending it all on additions to meet growing Wmart contracts. Now, they have to agree even though it costs them Y/4 to make the product (pine tree saplings). Wmart knows this, and knows that they now have the greenhouse in their pocket.
They have been varying on this formula by eventually dropping the contract entirely and buying the businesses out, creating "Great Value" brands.
The new experience with Wmart that I was talking about is related to these "Great Value" brands. Wmart is monopolizing markets, because they control the point of sale for virtually every grocery and many other products. For instance, they can choose to sell Barber's milk for $3, and sell their own low-quality milk for $2. Barber's may only cost them $1, and theirs may cost them $0.75. However, if people buy the Barber's anyway Wmart gains $2, and subsidizes their milk production. Eventually Barber's will go out of business and Wmart will hike their milk up to $4.
They are doing that with products all across the store, from Listerine to cane sugar. They control the market, so now they can even drive their own suppliers out of business. Once you have ultimate horizontal expansion, you can gain vertical expansion with ease. Sickeningly efficient, and the end result is that we drink crappy milk and pay a ton.