A reader recently alerted me to the fact that my images have not been able to be pinned to Pinterest, due to a privacy change made by Flickr, a site I pay for to host my images.
Typically I like to keep all my blog photos on the private setting with the exception of one or two; I do this for a number of reasons and Pinterest having access to them through my blog was never an issue.
Since this change I've had about a 30% drop in Pinterest traffic to my blog. True, my blog is not the most popular, but considering the rise in popularity of Pinterest, I consider it to be a valuable way of getting more exposure.
After spending the better part of the morning trying to figure out what needed to be done and emailing the help desk at Flickr, I finally have the solution:
Only a public image can be pinned. There seems to be no way around this. Images can be changed from private to public with a batch action and you will not have to replace the code to the blog post. (Going from public to private, or replacing the image will require code to be replaced.)
Additionally, you must either allow your public content to be shared universally, or change your license from all rights reserved to a creative commons (which you can do on an individual basis or a batch action).
Also, you may need to make sure your API settings allow your photos to be found by third parties.
Hope this helps any Flickr users who want their blog content to be Pinned!
You can find the official thread at Flickr here.