In February 2000, Amazon announced that it had been granted a patent on components of an affiliate program. The patent application was submitted in June 1997, which predates most affiliate programs, but not PC Flowers & Gifts.com (October 1994), AutoWeb.com (October 1995), Kbkids.com/BrainPlay.com (January 1996), EPage (April 1996), and several others.
Its amazing of the many affiliate programs that are out there where people are making a good living from them. For example the few that you mention that has such a great training model, wealthy affiliate tops them all because of the way this business is structure and I believe that wealthy affiliate has the best training program in the world when it comes to affiliate marketing. Thanks for sharing.
Google Adwords can be used to drive targeted traffic to a sales page. You simply make an ad in your adwords account then use your affiliate link in the target page URL of the ad. Obviously, you will have to continuously measure the conversions and see if the campaign cost is less than the campaign profit in order to keep the campaign running but I am sure you get the idea.
The problem with affiliate marketing, like many other home business options, are the so-called gurus and get-rich-quick programs that suggest affiliate marketing can be done fast and with little effort. Odds are you've read claims of affiliate marketing programs that say you can make hundreds of thousands of dollars a month doing almost nothing ("Three clicks to rich!"). Or, they suggest you can set up your affiliate site, and then forget it, except to check your bank deposits.