Here are all the companies Airbnb has acquired to help it grow into a $31 billion business

· Since its launch in 2008, Airbnb has gone from a startup renting air mattresses to a multi-billion dollar global travel company.
· After a wave of lukewarm receptions for tech IPOs last year, Airbnb announced its own plans to brave the public markets in 2020. 
· Investors wil be taking a close look at the company's...