20% of your time for personal projects

Im sure these are not homers, but actual time for them to play with their own ideas. But Google lets its engineers and other employees spend 20% of their time on side projects. According to Google’s Vice President of Search Products and User Experience, half of new product launches originated from 20% time. That’s a great return on investment, and I suspect it originates from the fact that employees have something to look forward to, and their job doesn’t become mundane. Looks like that is a good idea then, I have often thought that a lot of companies stifle the people with the ability to add value by creating a them and us mentality. The Google idea is food for thought. I wonder do they part own the project like a university would for an invention created as a uni project? Wikipedia post