This so called "investigation" of the Facebook app can be done much simpler. Locate the app in iTunes, rename the .ipa file to .zip, unzip and run otool and nm on the binary. The author list 18,000 header files which is not much of an investigation nor much interesting. Though the staggering number of classes does admittingly somewhat explain the enormous size of the FB app. I do not use the FB app, but generally it can be equally illuminating to look in the Resources/ folder of an app if you wonder where the size came from.