Also even given a trivial passcode, if you use "complex passcode" and the same 4-character passcode, you've vastly increase the key search space with a minor change to usability (esp. if you have touchID).
Having the password (in your mind and on your fingers) and the "sensitive information" ;- having them together in the same place at the same time is just asking for it really.
Look at this list of Soviet interrogation tactics and imagine how many of them could easily be used against you in your country's justice system: http://www.informationclearinghouse.info/article9236.htm
edit: link is to a low-quality site but the text is copied directly from http://en.wikipedia.org/wiki/The_Gulag_Archipelago
The researcher does recommend never surrendering your phone unlocked however - that guarantees someone can just hook it up to a USB connection, and tap "trust", and then proceed to pull all your personal info and credentials out.