Have you had this experience? You're shopping for something outside your area of expertise, and you hit a wall of mediocre websites. Each has too many products, each product described by 1 line of text and a janky 50x50 jpeg. None is quite what you're looking for, though you're sure the product exists. Eventually you find a site that has what you're looking for, but it's in German. But then you start for searching for that specific nomenclature, and you can eventually find a site in your language that talks about what you want, but doesn't sell it. They link to 3 online stores, 2 of which are broken links, and one of which is one of the janky sites you found in your first search.
It's like, the story of my life.
Now, go to http://www.mcmaster.com/ and try to find some piece of hardware, like say, a 3/8 hex nut. The site isn't perfect, but I'm betting it gets you there, and teaches you something about hex nuts along the way. The part I love is that if you search for a broad category, it lets you narrow down your search in a way that makes sense to you. You build your own decision tree, instead of being channeled down theirs. It is a very flexible process.
So, online shopping: who will fix it? Who will make the process work when I don't already know what I want, or how to describe it, or how to search for it? Who will let me buy something by teaching me what I want to buy?
*Amazon.com is OK, but not great. It's mostly usable, which is enough to make it the world leader. But it only covers a relatively small area of content.