Fluff companies sold to idiots by con-artists. Groupon continues to turn in losses, down from $12 billion at IPO to $4 billion and likely worth nothing.
Uber relies on a commercial advantage of offering a taxi service without the regulatory limits of taxis, but that won't last as they crack down on it, an an obvious taxi service.
Companies that make money hire fancy accountants to hide income cleverly, and keep their valuations trading in an income/profit range.
Companies that sell dreams hire fancy accountants to create income cleverly, and keep their investors hanging on with projected profits and world domination.