Similar rules from other companies, one of the search giants, have raised concerns after Russian internet giant Rambler Group claimed ownership of Nginx while author Igor Sysoev was working for the company. It owns the intellectual property rights of projects you created during your time at the company, and this provision also applies to your personal projects, as well as to new development work for older projects during your tenure.
Google may also find the scope of the rule too broad and unapproachable, so it has a procedure in place to allow employees to submit applications to take individual projects out of Google, but Google may not necessarily approve each application.
Hector Martin, a Google developer, posted a series of posts on Twitter describing his personal project experience. Before joining Google, he maintained two open source projects, AsbestOS (PS3 Linux) and usbmuxd (iPhone USB comms daemon). He submitted his application, and Google approved AsbestOS but refused usbmuxd without explanation, which led him to hand over the maintenance work at usbmuxd.
Martin’s experience with other open source projects is also due to Google’s rules.