With Apple’s App Store and the Android Market now literally filled with hundreds of thousands of apps, it’s getting increasingly hard for apps to stand out. And yet, every once in a while, an app will break out to become quite successful – at which point, we all start to wonder what’s so special about this particular new application and how others might replicate its popularity. Something of that sort is now happening with new and rapidly rising photo app Instagram, a photo sharing app that adds a retro style to the pics you take. It’s getting popular fast – it’s only been around for about a month and…