The "Follow for Discount" Shopify App lets you add a "Get a Discount" button to your store. When clicked, a discount box will be shown to your customers offering them a discount in exchange of liking your Facebook Page or following you on Twitter. After liking/following you the customer will get a Coupon Code that can be used during the Checkout process.
The app was built to be very simple and easy to use. You can add the follow for discount button on any page of your store and start getting more traffic thanks to your customers!