Ya, seems pretty odd. We'd have to see AirBNB's revenue to to see if its really worth that price. As well, I believe HomeAway has a higher number of listings than AirBNB does.

Initially AirBNB had the advantage that it allowed for one-time postings of a property (as HomeAway would charge annually to post a property). But HomeAway has recently added per-booking fee if you are only posting once or twice a year.

At this point, I feel like AirBNB doesn't offer anything HomeAway already does. So unless AirBNB has some amazing growth potential or revenue, I don't see $10bn being likely.