CodeCanyon - Social Coupon for WP v1.1.0 | 135 KB
Social Coupon for WordPress is a WooCommerce extension that allows you to easily add a social coupon system to your site that allows users to get instant discounts for sharing your pages. Social Coupon makes it super easy for you to gain thousands of new fans and followers for your brand, and increase your social media traffic. More shares = more traffic = more $$$$
How does it work? You can choose to show Social Coupon on your product pages, cart page, and checkout page. When a social action is completed, a WooCommerce coupon code of your choice will be applied directly to their cart.
DEMO:
http://codecanyon.net/item/social-coupon-for-wordpress/3417466