I want to see them start open sourcing more of their i18n and translation tools. Most people aren't aware of this, but one of the coolest problems you can work on at AirBnB is building out tools and features that let two people, who don't speak a common language between them, transact with one another. There is no other startup I know of as vested in solving this problem.
It's great to see AirBnb's open sourced work, and tech talks, etc. Kudos to them - I'm sure it helps a lot with recruiting. I used to work for a company in a similar space and looked to AirBnb with deep envy.