Like a love child of eBay and CouchSurfing.com or craigslist, AirBnB lets anyone that owns space fit for accommodating travelers - be it a couch in a small apartment or the master bedroom of a 19th-century castle - post that space as a listing on its website and connect potential renters to its respective owners. Once called Airbed and Breakfast in full, AirBnB aims to provide a secure online marketplace for these types of transactions and make people 'travel like humans' again. Now the startup, which came out of Y Combinator 's winter 2009 class, is making it easier for people who share interests (e.g. photography ) or have another connection with each other (e.g. alumni who've attended the same university ) to share travel accommodation and recommendations thanks to the addition of Groups .