Think of what eBay might do. With .eBay, the company becomes a registry that, like an apartment building owner, decides who gets an .eBay address and manages all the website names it signs up. Maybe that's anyone who wants to sell occasionally on the site. So instead of a convoluted website address such as http://myworld.ebay.com/abestshop4u/?_trksid=p4340.l2569, which only a mental contortionist could remember and would be useless to use in print material, you get OldBooks.eBay. Not only can you put it on printed material, but it can appear where those who might see it can still remember it, say, the side of a bus.
The ability to customize a 3D printed item before you buy it - just by using your browser - is an exciting option, one that takes advantage of 3D printing's ability to economically print one-offs with modest variations.