Airbnb, the service that lets people rent their houses, apartments and rooms over the internet to strangers, has taken a $500 million round of new investment which values the company at a staggering $10 billion, according to Techcrunch. It is not a surprise that the fund-raise or the valuation is that high — Airbnb is a transactional app and web site through which 11 million people have booked stays in 34,000 cities.