Re: Very sensible article
As you say, they don't talk about quite the same things so I shouldn't be too pedantic.
The key points I would make, though, are these:
Firstly, although the VCs who incubate and market these companies and the people who build them want us all to ignore the question of money because 'this is a disruptive new idea with enormous growth potential', their own keenness to monetise the investment demonstrates that people should be extremely wary. If money now really didn't matter then all of the people involved would be less desperate to IPO and make their millions asap.
Secondly, and more importantly, the problem with the 'web 2.0 allows us to disrupt the market and build a giant empire which will make us hugely profitable' business model is precisely that the internet makes building giant and giantly profitable monopolies which last for generations (IBM, Standard Oil etc.) much more difficult. Even before Facebook is reliably profitable there are a dozen good reasons why they might cease to be relevant in the near future and even Google face threats to their absurdly profitable search business because the monopolistic behaviour and vagueness in explaining their business model is more visible and so less acceptable than for a similarly positioned company pre-internet/
All of that means that even exorbitant growth doesn't justify a valuation which assumes the type of monopoly power Microsoft had in the 90s.
The venture capitalists who push these disruptive startups are glossing over the fact that it's the ease with which business models are disrupted which really makes the internet scary, because if they spelled that out then noone would buy shares in Facebook or Groupon at even a tenth their current valuation.
That's why this is a bubble.