They've surely realized very early on, they've just been trying very hard to be hush about it. Can't blame them, much as I dislike them.
I further contend there really is no solution. It's a war of escalation. We've seen it play out with SEO and search engines over the years. You can still "game" Google, but it's a lot harder to do it, the barrier to entry is a lot harder than it used to be when you could just list your site with a link farm. I am guessing that Amazon is in a similar war.