title: Using phone's unique device identification number instead of account
body: <p>I have an idea for my mobile app where it does not use traditional account like account username and password. Instead it will use device's unique identification number as an anonymous account.</p>
  
  <p>I have some questions.</p>
  
  <p>I have never developed a mobile device before so is it possible to get unique identification number on all platforms especially iOS and Android?</p>
  
  <p>Can I assume that all devices in the world have unique identification number and nobody could change theirs to be similar to other number?</p>
  
  <p>Will there be any legal or technical ramifications for using identification number instead of old-fashioned way of using account with username and password?</p>