9. Google Buys YouTube
Sale Price: $1.65 billion
Google turned heads in 2006 by making a year-old user-generated video hosting site its largest acquisition to-date. Detractors questioned whether YouTube, already facing legal battles from both movie and music studios, was worth the cash. Google doesn't release YouTube's finances, but today the birthplace of a million memes is the third most popular site on the Internet, after Facebook and Google itself.