Devina Divecha writes, in Pinterest — friend or foe?, "I cannot, in good faith, become a Pinterest user until the copyright infringement issues are resolved." She continues: "The website itself is trying to provide a temporary fix to those concerned about copyright by providing an “opt out” code for blog and website owners, who can incorporate into their websites preventing people from pinning their work."
Temporary fix? Never mind the "opt out" code being a temporary fix, Pinterest has the technical ability to easily block pinning from any website from their end. Is Pinterest bothering to tell people about this much easier fix for webmasters? No, of course not. Pinterest wants to make it as difficult as possible for artists whose content is infringed upon.
Anyone interested in having their website blocked from pinning doesn't need to bother recoding anything. Just write an angry letter to firstname.lastname@example.org and they will do it for you.