Most of them are US startups initially backed by venture capital (VC). Some of them are now worth more than $1 billion; others are planning for an IPO; and a couple of them have been acquired for a lot of money while generating little (if any) revenue. Most originated in social media, in the collaborative economy, and pretty much all of them depend on mobile as a significant and growing part of their business. They represent the typical attendees at the LeWeb conference in Paris, looking to become the next Facebook or Amazon in the next 10 years. Some other smaller and less well-known startups competing in LeWeb's startup competition this year may join this list: http://paris.leweb.co/programme/startup-competition
In fact, what they really have in common is that they are all digital disruptors leveraging digital platforms to create new experiences on top of connected devices. They are taking advantage of open development tools and free infrastructure resources to overhaul products, invert category economics, and redefine customer relationships. They are more agile than traditional companies. As my colleague James L. McQuivey stated recently, digital disruption requires an organizational fix if you don’t want your company to be disrupted.