I like your interface, very clean. How do you plan to monetize/keep-it-going?
I don't think you'll find many people willing to annoy their followers/friends with advertisements, even in exchange for some pocket change.
I'm not sure if that's what you meant but if so: Businesses are on Twitter/facebook to try to connect the current/prospective customers in order to encourage repeat business. Adding advertisements to short links would detract from that mission.
Seeing as a large number of people use ad blockers that's not a great UI experience - quite a few people could even click back/close because they think it is the page their visiting loading.
