Figure they do like many others anymore - just drop-shipping middlemen. I've run into it frequently.
No warehouse, no actual inventory, just some computer code on a server somewhere that accepts and order and passes it on to one of their wholesalers for shipment. Put a smallish markup over wholesale, and let the automation run. Customer complaint? Let it fall through an automated decision tree.
Where the model falls apart is that they either a) can't get inventory stock information from their distributors, or b) deliberately just mark everything in stock to catch orders. If the item happens to ship before the customer gets angry and cancels, great, it's a sale. If not, they aren't out anything.
As I understand it, Monkeyleg as doing the same drop-shipping middlemen thing, but without as much automation and much more customer service to get customers products from the companies that actually physically had them.