It is great blogging practice to comment on other people’s stuff, but it is against the law to copy and paste a large portion of what they’ve written. Always cite and link to the original source. How much is too much to quote? Try to quote no more than 15 percent of original material. Single digits are even better. Directly quote only the barest minimum you need to make your point. If you want to write a point-by-point counterattack of something someone else has written, write a very quotation-lite rebuttal that links to the original. Bloggers Must Disclose Payments for Endorsements – It’s the Law Most bloggers use blogging as a marketing tool to promote a product, service, mission, or expertise. The blog serves as a credibility, visibility, service, and sellability booster. But for some, the blog itself is the moneymaker. Some bloggers have blog “tip jars” for loyal readers to thank them for their great content, and some bloggers endorse other products or services in exchange for compensation (commission, sponsorship, free products, etc.). To keep blog content as authentic as possible, the Federal Trade Commission has mandated that bloggers must disclose payments for endorsements.
Most see this as a great rule, since bloggers will have to be transparent about their recommendations and readers will know what content is truly a recommendation. If the online marketing strategy includes making money from ads that live on the blog, then make sure it is crystal clear to readers that there is compensation involved for certain product or service endorsements.