The "120%" joke is very common within Google. Interpret that as you will. I don't know what you mean by social incentives. Don't expect anyone else to care abo

The "120%" joke is very common within Google. Interpret that as you will. I don't know what you mean by social incentives. Don't expect anyone else to care about your 20% project. It is quite feasible to bank up your 20% time and then ask for a few months of relatively uninterrupted work. If you're doing a blue sky project from scratch, that's the only way I think it can work. But seriously though, how long do you think it will take to make a prototype? If it's longer than three months of solo work I doubt you will ever get it off the ground, in Google or out. So if you have something you know you want to do, and can afford three months of unemployment, maybe you should do that instead. The experience will be worth it and it can only help your chances if you apply to Google later.