James Ball, at The Guardian, thinks that Uber's implicit $18bn valuation is "a nadir in tech insanity". His case is that tech firms are overvalued because although investors know this, they always assume there are other "suckers" they can palm their securities off on. That is, they think the other guys are "behavioural" (falling prey to the sorts of biases detailed in behavioural economics and behavioural finance) but they themselves are rational. Ball is responsible for some very good and important work, but I think this particular piece would benefit from the application of some financial economics.
It's always possible that prices are irrational. And because we can never test investors risk preference separately from the efficient markets hypothesis (the idea that markets accurately reflect preferences and expected outcomes) it's very hard to work out if prices are off, or just incorporating some other factor (usually risk). This is called the joint hypothesis problem. But when there are two alternatives, there is a reason economists put rational expectations in their models—it's a simpler, better explanation. Finding truly suggestive evidence of irrational price bubbles is the sort of thing that wins you a Nobel Prize not something that a casual onlooker could easily and confidently observe.
Ball might say that even if irrational pricing is rare because of the strong incentives against it in a normal market, there have certainly been episodes of it in the past. Quoting J.M. Keynes, he might say "markets can remain irrational much longer than you or I can remain liquid". He might point to the 1999-2000 peak of what's commonly described as the "dot com bubble". But I urge Ball to consider a point raised in this email exchange between Ivo Welch and Eugene Fama:
How many Microsofts among Internet firms would it have taken to justify the high prices of 1999-2000? I think there were reasonable beliefs at the time that the internet would revolutionize business and there would be many Microsoft-like success stories based on first-mover advantages in different industries.
Loughran and Ritter (2002, Why has IPO pricing changed over time) report that during 1999-2000 there are 803 IPOs with an average market cap of $1.46bn (Table 1). 576 of the IPOs are tech and internet-related (Table 2). I infer that their total market cap is about $840 billion, or about twice Microsoft's valuation at that time. Given expectations at that time about high tech and the business revolution to be generated by the internet, is it unreasonable that the equivalent of two Microsofts would eventually emerge from the tech and internet-related IPOs?
Has not the second wave of cyber firm success (Facebook, Google, arguably Apple) been even more impressive than the first wave? It may well be only 25% or 10% likely that Uber turns out to be one of these behemoth firms, through network effects, first mover advantages, name-recognition or whatever—but even if the chance is small the potential rewards are huge.
But Ball may point out that even if this is true, in the (putatively) 90% likely scenario, of Uber being a failure, then all this capital is being wasted. It could be put in the projects he prefers: "green energy, modern manufacturing, or even staid-but-solid sectors like retail". Even if rational expectations—the idea outcomes do not differ systematically (i.e. predictably) from predictions—and the efficient markets hypothesis are not violated, and risk-adjusted expected (private) returns are equal across industries, it might be that social returns from these staid-but-solid sectors are higher—after all, lots of capital is being apparently wasted when so much goes to Uber.
This does not obtain—from the prospects of society, Uber could deliver huge welfare gains. If it does turn out that Uber has enough in the way of network effects to generate returns justifying its price tag (or more) then it would have to create lots of value, by saving taxi-consumers serious money. If they are using less resources to create the same amount of goods, then they are making society better off. Since society is big and diversified, it can afford to be relatively risk neutral (at least compared to an individual), and take even 9-1 punts on the chance that one memorable, semi-established network might be a particularly good way of running a taxi market.