Daniel Amitay collected a set of four-digit passcodes from iPhone users using his Big Brother Camera Security app (which Apple has subsequently banned from the App Store). If you have an iOS device and you lock it using a four-digit passcode, this article makes interesting reading.
Formulaic passwords are never a good idea, yet 15% of all passcode sets were represented by only 10 different passcodes (out of a possible 10,000). The implication? A thief (or just a prankster) could safely try 10 different passcodes on your iPhone without initiating the data wipe. With a 15% success rate, about 1 in 7 iPhones would easily unlock–even more if the intruder knows the users’ years of birth, relationship status, etc.