[lukeholder]

I would suggest you simply ask the user for the information you need in order to give them something, then offer facebook as a simpler way to give them that.

I mean, if you are getting access to their FB accounts to see what they like, why not put 5 input boxes down the left side with something like "Name your 5 most favourite things" with a submit button.

On the right have something like: "Or sign in with facebook and save some time!"

If they like what they get with the inputs on the left, they are more likely to give you access to their facebook data to enjoy the experience more.