Copyright:What Makes a Use “Fair”?: Here’s a well-written explaination of what makes usage of a copyrighted work legal under the “fair use” provision.
What makes a use “fair”? There is no simple formula. Some uses are favored in the law. They include criticism, comment, news reporting, teaching (including making multiple copies for classroom use), scholarship, and research. But these uses are not automatically deemed fair, nor are other uses automatically deemed unfair. Fair use depends on the facts of a particular case. The law provides four factors that must be considered in deciding whether a use is fair.
I wonder where the above quote fits in? We make moeny from ads, so it’s commercial use. The “amount and significance” is small. Does the above quote, or any quote from this blog or any other, detrimentally affect the marketability of the work? I don’t know — this is why we have copyright lawyers.