the PIN is also useful when downloading applications. sometimes the application is "registerred" to a particular customer. The manufacturer doesn't want you buying an application for $10.00 and then sending it to all of your friends. they want $10.00 from each person. So, when downloading the app, you'll be asked for your PIN sometimes and other times they'll issue you a code to enter to "turn on" the application. So, it's useful to know your PIN so over the air (OTA) downloads go smoother.