Date: Oct. 3, 2002

Acquired for: $1.5 Billion

After failing to achieve success with its own money transfer service, Billpoint, the ecommerce site decided to buyout the middle man in its operation, PayPal, which already accounted for 60 percent of business. The merger became eBay's smartest investment and a turning point for the tech industry. How so? On top of PayPal generating 40 percent of the business' earnings as of 2012, a new breed of Internet entrepreneurs known as the PayPal Mafia would emerge. You might know them as Reid Hoffman (LinkedIn), Elon Musk (Tesla, SpaceX), David Sacks (Yammer), and YouTube's Steve Chen.