5AirBnb - $2.5 Billion
The couch surfing pioneer is live in close to two hundred countries. If it was a hotel, it would be booking over 60,000 rooms each night. The company has a valuation of over $2.5 billion. In early 2013, Airbnb had over $1.7 billion in sales. Its expansion rate, too,
has enjoyed exponential growth. The service could only benefit from the kind of exposure and integration that Facebook could grant it, but there is no deal on the table at the moment.