[jrockway]

Isn't that kind of what Shopify, Fast, and some other company that I only heard off because they laid off half their staff doing?

I haven't researched the industry extensively, but I'm guessing that companies like to keep customer data to themselves and curate what they think is the ideal checkout experience. (Everyone should copy McMaster, though.) That's why you see companies happy to delegate the financing involved in buying their products to credit card companies, but still make their own website/checkout/fulfillment rather than letting, say, Amazon do that for them. (Shopify does seem to have quite a lot of traction, however.)

[lisper]

None of those companies are syndicates, i.e. none of them are owned by the retailers they represent. They're trying to just be middlemen. That won't work.