I wonder if something like exists or is offered to me as an option to use. As I get my Amazon store front set up, I think it would be very helpful to me and customers if I had the ability to include place on the page where someone can enter a promotion code or the name of someone who referred them to my product. The intention of this is to offer word-of mouth-advertising. I hoped I am explaining this feature using easy to understand terminology. Let me give you an example. You hear from time-to-time in a commercial on the radio or even in an ad on a web site to "add promo-code..." in order to get a discount or something. This, I assume, is a way to track the effectiveness of advertisement and which advertisers are doing a good job at driving traffic. That would be one good use. But I think another good use is to give word-of-mouth advertising a boost.
There's no point in this.
Said differently, this nullifies the use of promo codes.
With Amazon, there are near zero analytics.
You're only hope of crude tracking is to keep your promo codes private, only provided in specific email or direct mail copy, to have some sloppy guess about who's buying your product.
Best to also expire these quickly, because if you leave running for years, someone will pass this along to their list, which passes it along to other lists.
Long term promo codes dilute data to an unusable point.
Tip: Also, include some device on your product to drive people back to your site.
Since you provide no information, no clue as to how to structure this device.
Example: Say you're selling bagged Maca on Amazon. One each package you'll include something like...
Email email@example.com for a free recipe book on 101 Maca recipes + energy boosting hacks... in 101 easy to implement email messages.
Some device to collect purchaser information.