Does it really make sense that Twilio has gone up so much since its IPO? Is it likely to crash hard back to earth in the next year? Who knows, maybe it's one part sentiment, one part broad market euphoria, one part hitting their next quarterly numbers, one part story, etc.

If you were to run almost any kind of reasonable attempt at analyzing and valuing Tesla based on what it should maybe be worth via comparables, you'd get a figure dramatically lower than it is today. Do you compare it to a solar company? To Fiat? To GM and Ford? To Porsche? Doesn't matter, every example gets a Tesla worth far less than it is today. Public shareholders disagree however, they think it has a very bright future.

The same has been true of Amazon for most of its existence. Try to apply any of Target or Walmart's valuation ratios to Amazon, and you'd have to reduce the market cap by 3/4 at least. Should Amazon be worth 50% more than Alibaba? Investors think Amazon is going to grow a lot yet.

Does Google's (ever slowing) growth rate really justify a PE ratio 2.5 to 3 times that of Apple? Microsoft hasn't really grown its profit level in years. Should it have a 20 to 25 PE ratio, roughly twice that of Apple? So far as public shareholders are concerned, these things make sense today.

So Uber is really worth $28b, not $62.5 billion? Good luck with that.