Compared to some of the overt cruelties we see in the world? It's pretty subtle. The psychological, financial, and social impacts it has on workers and their families, once again, if left unanalyzed, pretty subtle.
I don't know. None of this is surprising. Everyone knows that Wal-Mart benefits from Foodstamps both in the sense that they are used to subsidize worker pay and at the same time as payment for goods Wal-Mart sells. In the context of this article I can make a statement such as "It only makes sense that Amazon would try and copy that business model" and once again, I've stated nothing profound, only the obvious. You bring these ideas up in a conversation and people respond with "and water is wet." People don't really stop to think about how fucked up all that is, at least, not on the regular.
It's like we all willfully trivialize the issue because in doing so, it's easier for us to ignore it, or at least, ignore the idea that we should do something about it.