Affiliate marketing is also called "performance marketing", in reference to how sales employees are typically being compensated. Such employees are typically paid a commission for each sale they close, and sometimes are paid performance incentives for exceeding objectives. Affiliates are not employed by the advertiser whose products or services they promote, but the compensation models applied to affiliate marketing are very similar to the ones used for people in the advertisers' internal sales department.
Many affiliates struggle to make enough profit from the sales they make to allow them to reinvest that money into more content or marketing. Once you do find a product that people can and will buy online, make sure it offers enough commission per sale to make it worth your while. There’s little sense in promoting light bulbs for 1% profit per sale.
Internet marketing is such a huge space indeed, for both companies marketing their products / services online, to affiliate marketers promoting products / services on behalf of organizations. Just type in just about anything in Google / Yahoo / Bing and you will be flooded with sponsored ads. Go beyond Google, and into social sites such as Facebook and soon Twitter. TONS of advertisements. The amount of e-commerce conducted online nowadays is just massive, and the amount of advertisement spend driving traffic in this space extremely high. No doubt there are tons of ethical or un-ethical affiliate marketers driving traffic of both real products or scam products. The Federal Trade Commissions are starting to notice this and are also commencing cracking down on scams or unethical ways of promotion such as setting up of fake blogs or news websites with the sole intention of promoting products. But internet / affiliate marketing is most likely here to stay as the world increases adoption rates for online transactions and promotions.
I would like to add that for information products, a lot of the time it’s pretty easy to rank for “information product review”. I recently did a review of a popular ebook that is a month long discipline program. I went about it by doing the actual program and documenting everything. At the end of the month I wrote up a 2700 word article summing up the whole experience.