The iOS data protection API and its implementation are fairly well documented, but it is only really useful if apps actually use some level other than NSFileProtectionNone for their files.
Is there any information on what protection level the stock iOS apps use for various data? Apple mentions that the Mail app uses the "Protected Unless Open" class for attachments downloaded in the background and stores and stores messages protected with NSFileProtectionComplete, but says nothing about other data like contacts, photos etc.
What about third-party developers; is there any research on how common the use of data protection is with popular apps? For iOS 7, Apple mentions that "[a]ll third-party apps now have data protection enabled automatically", but I wonder if that applies to "legacy" apps as well, and if some even actively disable the protection.