title: Getting a facebook profile picture from an email address
body: <p>I'm trying to get a user's facebook profile picture based on their email address. Effectively, I want to offer my users the option between using Gravatar for their image, or Facebook. However, the only way I know of to get a user's facebook image is via:</p>
  
  <p><code>http://graph.facebook.com/[FBOOK USERNAME]/picture?type=large</code></p>
  
  <p>Since the usernames may vary between facebook and my site, I would like to do this via email address rather than username. How do I query for someone's facebook profile picture via email address?</p>