Facebook & twitter icons still appear through out ios even if you don't sign in to these services in the settings. Whether it be for a bookmark or a photo there is still twitter & facebook icons in some options menus. They shouldn't be there imo.
I was going to suggest this over on the apple site but they don't have an option for iOS. Just a few apple made apps and individual devices.
(Bottom of apple page "contact us" then "product feedback" on the lower right side.)