"Yet HN comments are vastly inferior to Reddit's when regarding anything to do with economics."

I find that HN is pretty weak on economics. But it's a tech blog, so ...

And I'm not so sure that 'business ideas' are about economics. Usually, they are simply about doing things using newly available technology, in ways that are obvious in hindsight.

I don't think that AirBnB conceptually is rocket science - it's the great experience they provide for everyone. It's really well put together. AirBnB done by a lesser team of people would be something you never heard of.