In 2006 the biggest music videos on YouTube were uploaded by fans with usernames like "sillykat2008." Google bought the site anyway for $1.65 billion, got sued for $1 billion within five months, and turned the evidence into a $60 billion a year business. The story is wild. Viacom's lawyers counted 160,000 unauthorized clips on YouTube, viewed 1.5 billion times. Their argument was simple. The entire site ran on stolen content, and Google knew it when they wrote the check. They were mostly…