Facebook phone features:
Ringtone randomly changes to something embarrassing, rude and/or innapropriate when in public.
Texts are randomly CCd to members of your phonebook, though priority is given to family members when dodgy pictures are attached and spouses/partners when an affair seems to be taking place.
On leaving a 100M radius of your house the phone immediately broadcasts a "please rob me" text to all the scallies in the area.
Now and again your entire phone book will become searchable to anyone else with a Facebook account.