I looked at the code that might be causing this error, and the function is declared twice in the latest version of Jetpack, just as the error below says. Anyone else seen this?
[30-Jan-2014 19:58:03] PHP Fatal error: Cannot redeclare youtube_sanitize_url() (previously declared in /wp-content/plugins/jetpack/functions.compat.php:56) in /wp-content/plugins/jetpack/modules/shortcodes/youtube.php on line 132