Using Social Media to Drive Pledges

Hi all - has anyone had any experience with or any info on the success of using social media as a platform for pledging? Eg) if we want someone to pledge to keep their cat inside at night, the pledge would be you take a pic of yourself with a cool image, post it to your Facebook with a hashtag which prompts the image to be placed on a visible screen.

Any thoughts would be awesome, thanks!
Beck
Melbourne Zoo

Rebecca Levy
Interpretation Manager
Melbourne Zoo
Australia
www.zoo.org.au