Bebo
Social network from 2005 that dominated Britain and Ireland, and which AOL bought for $850 million just before the whole category moved to Facebook.
Michael and Xochi Birch built something resembling MySpace but tidier: profiles with swappable skins, a friends list, and small social mechanics like Luv that you handed out to each other. In several countries it was the obvious platform among teenagers for a couple of years. The AOL deal in 2008 became one of the era's most-cited overvaluations — two years later the company was sold on for a fraction, and in 2013 the founders bought their own creation back for around a million dollars. The name has since been reused for a couple of different video services without the old network returning. The story is a clean lesson in how fast the value of a social network can go from everything to nothing.