this post on "how twitter was born" is making the rounds; thanks to Prentiss Riddle for alerting me to it. The best quote from it is the use case that involves the worst possible internet device in the world: text messages from a mobile phone.
I remember that @Jack’s first use case was city-related: telling people that the club he’s at is happening. “I want to have a dispatch service that connects us on our phones using text.” His idea was to make it so simple that you don’t even think about what you’re doing, you just type something and send it. Typing something on your phone in those days meant you were probably messing with T9 text input, unless you were sporting a relatively rare smartphone. Even so, everyone in our group got the idea instantly and wanted it.
As a point of comparison, here's part of the origin story for Gopher, the early 1990s internet system:
"Full-text searching was like a new thing under the sun five years ago," notes McCahill.
The two, with assistance from the newly formed Gopher Team, fine-tuned the prototype as music from Nirvana and Mudhoney blared in the background.
"It was a fun time," recalls team member Torrey. "It was a lot of late nights and weekends and a lot of beer, pizza and speed metal."
Eventually, the team needed some files to dump into their baby Gopher so they could demonstrate its text-searching capability.
"We took the Usenet (the Internet's newsgroup system) cookbook and put that into it," says McCahill. "That was the first thing - so first the Gopher was serving recipes up. We figured everybody ate, and it was a good way of illustrating what full-text searching could do."
If you were looking for recipes with eggplant, you simply typed in the word and the application would locate every eggplant reference - a dazzling capability in 1991.
nothing quite like having a real use for the system you build while building it.