I always thought gmail was an example of an employee coming up with an idea, and having automatic-permission to explore it due to Google’s 20% time. It is constantly referenced in articles about the policy.
But there is some nuance here. It turns out Larry Page asked Paul Buchheit to explore email:
Larry Page assigned the project to me. He said, “Build some kind of email something” and chose me because I had an interest in email. I tried to create a web-based email service in 1996, shortly before Hotmail, but didn’t complete it.
Interesting. This takes away one powerful piece of evidence often used to justify policies that enable employees to pursue their own innovative ideas on company time. In this case there was an executive sponsor right from the beginning.