I never set out to make any money blogging, and despite an occasional affiliate link here and there, this remains my philosophy. I originally created my affiliate accounts so that my own piano students could use links I set up (mostly CDs and sheet music) at students.twedt.com. I reinvest all commissions into sheet music for my teaching library. I love to share my ideas freely with the world, but if you had affiliate accounts and you were creating links to Amazon.com and other places you had affiliate accounts with anyway, wouldn’t you want to make them affiliate links while you’re at it, too? Might as well!
Also note that my affiliate links are cloaked – for example, Amazon links point to students.twedt.com instead of Amazon (but are still redirected to Amazon), so to make the links easy for my readers to pick out among other links, they always appear green. The cloaking is only to protect my affiliate links from being hijacked by viruses on my readers’ computers.