title: What's the length of the new app-scoped User IDs
body: <p>In Graph API v2.0, Facebook introduced new "App-scoped User IDs". In <a href="https://developers.facebook.com/docs/graph-api/reference/v2.0/user" rel="nofollow">the documentation</a>, the ID field was changed into a string, however the length of the new IDs is uncertain.</p>
  
  <p>Any insights?</p>