Suppose you have an app that uses a proprietary authentication system based on HTTP headers and further suppose that the authentication info is hard-coded into the app (I don't know how you would do it otherwise). It hits a web service via SSL.
I do not think that it would be possible to sniff out the headers (correct me if I am wrong) but would it be practically possible for a motivated user to decompile the app and get the API key somehow? How does this vary between iOS (Obj-C) and Android/Blackberry (Java)?