That's easy: This person has no idea why Walmart is successful. Walmart's success has little to nothing to do with convenience. It has everything to do with economies of scale, being able to apply pressure to your suppliers, and efficient inventory tracking and prediction. The proposed website benefits from none of these...
That's why they're so profitable, but that's not why customers like them, at least not directly. Those things all contribute to low prices, which is one of the things he lists. All of the things you listed are benefits of extremely large scale, but Walmart wasn't born being huge. How did they get there?
I disagree. In the physical world, a "one-stop shop" like Walmart adds value because it costs time to travel between many different stores. What our author fails to realize is that there are already "one-stop shops" on the web: namely Google and Bing.
Even if you have to go through the arduous task of typing a website into your browser's address bar to get from YouTube to eBay, it's still a fraction of the effort required to get from Ace Hardware to Target, no matter how close the stores are situated to each other. The Internet doesn't need a one-stop shop as badly as "real life".
If that was THE website to go to for all of the services they offer, saving a couple seconds of typing might be advantageous. But they're not. Why should people switch? It's not particularly superior, as far as I can tell.
I applaud the effort, but will most likely never use it, and I doubt I'm alone.
I'm not sure on you guys reasoning, but this could work. You can't get a job on Facebook, or post your classifieds on Google, or Fiverr on YouTube. If it becomes integrated seamlessly with one login and you can do the same things as the other sites then it may work...just maybe, but I don't think this guy really knows what he is doing.