It seems like such an obvious idea, it's hard not to wonder why someone didn't think of it before. A website that allows people to open up their spare rooms to travellers; couch surfing for people with money. A centralised BNB website for people who do not necessarily run bed and breakfasts—sounds like a no-brainer, right?

Yet when Airbnb set up a website to do just that and went in search of funding, they could barely get a return phonecall from the angel investors they contacted. (Ashton Kutcher, who has become a self-styled angel investor, was one of the original believers in the idea. You can watch a video interview with him about the investment here.)

Now, on any given night in New York City, there are more people staying in homes through Airbnb than there are rooms in the biggest Manhattan hotel - and, according to TechCrunch, the founders are in the process of closing a $100+ million funding round.

Founder Brian Chesky said the idea for the site came when he and friends needed to make rent during a big developer conference. They knew hotels were booked out in the city for the duration of the conference, so they decided to pull out some airbeds (hence, the 'air' in airbnb) and rent out the space - effectively killing two birds with one stone.

A quick look on the Airbnb website shows there are already over 200 listings in New Zealand alone. Prices offered range from $10 per night for a place in Dunedin, to an ambitious $2,000 per night for a room near downtown Mount Maunganui.