title: Android GCM topic subscription limit
body: <p>With the introduction of topics in android gcm I was evaluating this option to easen the work that should be done to mantain in sync our server with some subscriptions. </p>
  
  <p>However I have read in the documentation that the use of topics is limited to 1 million subscriptions. Does this mean that you can't have more than one million users (with one or more topics) or that you can only have 1 million topics subscribed (for example 100.000 users subscribed to 10 topics each) ?</p>