Michael Nielson: "Ward Cunningham invented the first wiki because he was tired of responding to user’s requests to update a website he ran. To save himself time, he made the page editable, and told them to update it themselves. He was shocked when this small change utterly transformed the dynamics of the site.

One of the first widely used pieces of blogging software, Blogger, was originally a small part of a much more ambitious project management system. The project management system never caught on, but Blogger took off.

The team that developed Flickr wasn’t originally building a photo sharing service. They were building a multiplayer online game, and decided to let players share photos with one another. When they realized the players were more interested in sharing photos than playing the game, they dumped the game, and built Flickr."