It depends what you're after. Some people would rather a guaranteed lower income, rather than the chance of the big time. 37s have gone for the former, Digg+Facebook have gone for the latter.
Both are valid strategies, but the latter has far more potential upside (With way more risk). That's probably why it gets more press.
Who wants to read about another software company that sells products and makes a few million?
I'm not sure I buy the equivalence of no revenues = higher upside. There are plenty of companies that got big & famous by making products & selling them. These include software companies.
Sure there is something you might call a 'type' that can be built on your latter. But it's not the only type.
Digg and Facebook both have pretty good revenue. They just have stupidly high costs.
Well I suppose the goodness of the revenues needs to be weighed against the stupidity of the costs.
They are closer to being a "no ruckus" businesses than the others.