"We use Facebook only for identification. No sharing without your permission (promise!)"

While Lookmark may intend to follow all honorable practices, I'm curious if there are things Facebook can decide to do to subvert this.

IOW, does Facebook track the use of an account for Lookmark identification? Are they tracking when a user signs in to Lookmark?

Just how much does Facebook get to know about a user's use of Lookmark?

Thanks, BTW, for offering a non-FB way to sign up.