5. Yahoo Buys GeoCities
Sale Price: $3.6 billion
A GIF-laden online community that emulated real-world neighborhoods, GeoCities was the third most visited website in the world in 1999, averaging 19 million unique visitors per month. When Yahoo! came knocking, the Los Angeles-based company collected a $3.6 billion pay check. But GeoCities' limited functionality and high server costs meant that it bled users and cash as time passed and "Web 2.0" began to flourish. By the end of 2009, Yahoo shut down the service in America completely.