Technology: Silicon Valley 'unicorns' face hard reality

The headline valuations of some private tech companies are being tested by their IPOs, raising fears of an imminent correction, reports Leslie Hook. Numbers such as Uber's $50bn, Airbnb's $24bn and Snapchat's $15bn became symbolic of the huge ambitions of this generation of start-ups. But they are not all they seem For information regarding your data privacy, visit