Uber, the five-year old startup running a popular app matching drivers with consumers, is once again the world's most valuable startup. After the last round of funding, the company is now worth $50 billion. Uber is followed by Chinese smartphone vendor Xiaomi ($46 billion) and Airbnb ($25.5 billion). The Wall Street Journal currently lists 108 so called "Unicorns", companies valued at $1 billion or more by venture-capital firms. Most of them are U.S. (72) or Asia based. Only nine of them are European.