incrediBILL - 6:00 am on Sep 8, 2012 (gmt 0)
It's easier just to block people from pinning stuff from your servers in the first place.
Of course then you have to block the content from Google cache, Google images, Bing images, etc. and the internet archives. All doable and way cheaper than filing out DMCA or dealing with lawyers.
Remember, if you want to protect your content, being proactive is always cheaper than reactive.
However, I'd just slap your domain name in all the images and let them pin away as it's free advertising.