The McDonalds/Amazon effect: Familiarity breeds temptation

The NYTimes has an article about the forthcoming Babies R Us redesign. Toys/Babies R Us has partnered with and the ecommerce offering of the R Us stores will be rolled under Amazon. The article talks about familiarity and the McDonalds effect. "The reason you go into a McDonald's when you are in a foreign country ... is you know what you are going to get, and you know how the french fries are going to taste. The reason you like a store to look like Amazon is because then you know how to navigate it comfortably." I see the point that familiarity makes for a comfortable and maybe more tempting shopping experience. But following this argument, is the best design direction for ecommerce interfaces to start with tabs and grow their product offering until the tab metaphor no longer supports the information architecture well? Personally, I think the current Amazon navigation experience has gone down the drain since they expanded beyond the available horizontal space afforded by tabs as they moved to become the Walmart of the Web. Sure, the "Store Directory" and "Browse menu" afford access to the many new categories of products on Amazon, but I personally wonder, when I think about the growth of their product inventory, how they will continue to make it easy to shop without feeling overwhelmed by the navigation. The article ends with a final and telling comment from the shopper they interviewed about her shopping experience with the new Babies R Us/Amazon site, "... it still took me twice as long to shop. Next time I'm going back to my regular store." But she may be the exception. I'm sure Amazon might say that she spent more time because she lingered and surfed Amazon while shopping -- and that kind of behavior leads to add-on sales.