The first version was built with Facebook login on purpose, because we offload the social graph building to FB. Destinations are suggested based on where your friends currently live, and where they've previously been or want to go in the future.

It's not just about not bothering with user registration and passwords, it's about using the data from FB to give users added value.

We are in the early stages of building a completely non-social experience, including possibly a fully-logged out mode, which will use even more signals to suggest destinations. We don't have an ETA to announce for this as of yet.

-Luka (Hitlist)

That's a shame, because I don't have a Facebook account and never intend to.