This would make more sense to me as a tool for companies to discover conversations around their products and engage, not just another way for Bieber to check in with his fans. Definitely another attack on Twitter, though.
Here's a new UX question: "how would people use our app if they were super famous/influential?" I wonder what's actually different. A higher threshold of activity before sending push notifications? Multi-user account management so your PR/media team can post on your behalf?