Ask HN: how to find a users fb friends who have visited a place?

We're working on a travel startup - WanderShip that helps users search & plan their own holiday itineraries. We're looking for ways by which we can enable users to find their friends who have visited a particular city or country.

We've already checked FQL & Graph search but have not been able to find a way that we can get this data. Any one out there who has worked on this, or can offer any leads as to how we can approach this?

Gogobot and TripAdvisor do already have this feature, but it seems that they provide this with user data they have collected themselves.

Is there anyway of doing this with fb or leveraging any existing data?