Start-Up or Hoax? In Silicon Valley, Hard to Tell

Last fall, digital designer Alex Cornell had an idea for a spoof on Silicon Valley. While goofing off at work, he made a video to promote an imaginary iPhone app he called Jotly that lets people assign grades to anything they can photograph: tree leaves, messy desks, ice cubes, whatever.

The thought was: "Let's think of the most ridiculous possible app that no one would ever consider a real thing, and make that," says Mr. Cornell.

Silicon Valley took his joke seriously.