The problem with competing with AddThis and ShareThis is that they're dirt simple to slap on a page and free (not to mention they target more than just Facebook

The problem with competing with AddThis and ShareThis is that they're dirt simple to slap on a page and free (not to mention they target more than just Facebook). The advantage you have is that their target is sharing web pages and your target is sharing products - so make your widget dirt simple, free, and very good at sharing products. Then add things like discounts and analytics to a premium plan.