Trackword only uses your data for the game. It won't be sold or transferred, and Trackword only uses what's mentioned below; please do read this (short) policy.
Currently, Trackword does not show you the name/picture of people in the same game as you, unless you are friends with them. This is because, although that data is public, friend connections are not; and you might be able to infer who is friends with who from which players are in a game. Facebook's policies do not seem to require this, and this may change in the future should it appear that the benefits are sufficient.
When you play, Trackword stores your Public Data (defined above) and your list of friends. Trackword stores this rather than requesting it from Facebook every time because this makes a huge difference to the speed of the game.
Facebook's Platform Policies say that "You may cache data you receive through use of the Facebook API in order to improve your application's user experience, but you should try to keep the data up to date." Trackword gets updates from Facebook in order to do just that, updating its cache automatically when any of this information changes.
If you de-authorise Trackword:
If you re-authorise Trackword, it will store your friend list again, and you will be able to see your original game history.