How big is YouTube? Really BIG! As YouTube passes it's sixth birthday, there are 3 billion videos viewed each day, an increase of 50% over a year ago. 48 hours of video is uploaded to YouTube every minute, an increase of 100% over 2009.

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Source: ReadWriteWeb & YouTube
http://www.readwriteweb.com/archives/YouTube_sees_3_billion_views_per_day.php