How effective do you earnings by using amazon.com..?

If you mean their Amazon associates program, I guess I would say it's moderately effective, but in my case, I don't have high traffic sites to post links to, so I mostly rely on my own purchases for commission. But I believe if you have a high traffic site, you can probably have decent earnings if you use all the tools available to create effective affiliate links that will attract your web visitors and generate income for you.