The foundation of this whole bubble is too much (often its not that much) growth and no revenue or even future hope of revenue what-so-ever.
In short, there's a lot of bullshit start ups out there.
It'd be interesting to hear what 37s make of this, as it seems like they went for revenue rather than growth.
Personally I agree with the growth then revenue strategy, but I guess it depends on what you want to create, and what size market you think you could get.