You first point is a good point but... > I heart Airbnb but the idea that it doubled in value in less than a year and is worth almost as much as say Marriott,

You first point is a good point but... > I heart Airbnb but the idea that it doubled in value in less than a year and is worth almost as much as say Marriott, which owns real estate, generated almost $2 billion in EBITDA in the past 12 months and returns cash to shareholders in the form of a dividend, is absurd. Apple, a mega-cap company, has doubled in value in the last 3 years. That's somewhat "scary". On the other hand, it is completely normal for a startup to double in value in 1 year. Arguably, pretty much all moderately successful, venture-backed startups will reach that growth rate at some point. A conservative example: startup gets seed funded at a (say) 200k valuation then, 8 years later, gets acquired for 50M. That's an annualized 99% per year. Of course, homeruns like Google, Facebook, etc, had years with growth much higher than 100%.