Hi, thanks for your kind opinion ;)
About your problem: the share button at the bottom looks like this in the html code:
<img src="http://trinidadpena.com/blog/wp-content/uploads/2012/12/share.png" alt="Share" />
so it doesn't have a custom class added. To disable the pin it button on this particular image using disabled classes setting, the html code of the image should look similar to this:
<img src="http://trinidadpena.com/blog/wp-content/uploads/2012/12/share.png" alt="Share" class="nopin" />
where nopin is the class name mentioned in the disabled classes setting of the plugin.
It's possible that you won't have the ability to modify the html code of that image (e.g. it's generated by a plugin) and that's why in about a week I'll publish a new version of the plugin, where you will be able to specify the minimum image size below which the button will not show up.
Hope it helps.