[vladd]

Maybe not a 1st degree friend but a friend of a friend or something like this.

A feature that finds out the "shortest chain" friend that rents out an apartment in your destination city would be interesting. But you need a social graph for that.

[jacquesm]

Sounds like a facebook app worth making. Rent out rooms to people that are at most 3 hops removed from you on FB?

[mriley]

Check out SecondPorch (secondporch.com) for a pretty nice execution of that concept, built around FB Connect.

[quizbiz]

If I was Airbnb I would acquire the above.