In addition, the internet allows you to contact your customers more in comparison to how you would contact them traditionally. Online communication is more affordable than traditional communication methods such as sending mail and printing brochures. For example, you can send the same information in an email rather than a mail-out, saving you on printing, paper, and postage.
If you’re in the “how to make money online” market, you’ll make more in affiliate programs than Google Adsense or most other advertising programs, simply because of the points Yaro mentioned. Affiliate income is also one of my biggest sources of income. I wrote this short article of affiliate blogging tactics: http://www.easywordpress.com/labs/affiliate-product-blogging-model-explained/