If you use dynamic og:metags the head section can run quite huge beside the youtube way loading a json head. there is a nice option via javascript to load it after page load idea suposed by

Ching-Lan HUANG

digdog.thumbler.com

adding the title after the page load example

<script type="text/javascript">
// <! || document.getElementsByTagName('body')[0]).appendChild(meta);    
// ]]>
</script>

The Og:meta not only get read by Facebook robots also Google will index and show related to your og:meta type what and who it will show your content in the search.