Silicon Valley mulls 'unicorn' invasion

Proliferation of billion-dollar startups raises eyebrows, concerns in fast-moving tech sector

When social media software firm Sprinklr unveiled its latest funding last month, it vaulted into the club of "unicorns", or tech startups worth at least $1 billion.

That came just weeks after Slack, which makes a business software collaboration tool, entered the group which includes well-known names like Uber and Snapchat