Celebrate King's Day with TNW 🎟 Use code GEZELLIG40 on your Business, Investor and Startup passes today! This offer ends on April 29 → You know an app is on its way to going mainstream when a major brand like Starbucks has its own account. There’s simply no denying Instagram‘s popularity. In fact, it looks like the app just got a little bit more popular when Justin Bieber shared an image of LA tr