I created an app that gets the list of friends from a Facebook account, then stores a partial record of friends' data (just the name and the uid) in a SQLite database.

I am unsure as to what extent this could be a problem of any kind regarding privacy and such.

Would this even be against Facebook rules or something? 

Don't mean to be rude or anything but please don't reply with an answer such as "why on earth would you want to keep a local list of friends". Just assume there's a good reason.