I just noticed Pinterest created a feature to disable pinning on any and/or all pages on your site. All you do is add this “meta” tag to the header of the pages you want to disabled pinning on.
Now any time tries pinning an image on the page via the bookmarklet or by adding it by URL on Pinterest.com, it’ll popup a message like:
“This site doesn’t allow pinning to Pinterest.”
Note any “Pin It” button on the page will still work. We’ll have an update soon that will address hiding the button on a per page/post basis.
In WordPress you can use the Meta Tag Manager plugin to do this if you want it for your whole site.
To see Pinterest’s official explanation of this go to Pinterest Help and look down towards the bottom. You should see the question:
“What if I don’t want images from my site to be pinned?”
Update 2/20/2012: Pinterest blogs about it and why they introduced this.