I wrote a project at Google that had nothing to do with Google's business, in fact, they explicitly had chosen to not get involved with that whole area at all (Bitcoin). I applied for ability to open source it under the Google name and was denied, I asked for a copyright release back to me and was also denied. The open source programmes office had decided they wanted my project dead and preventing me from doing anything with it was their tool.

Eventually I was able to get these decisions overridden by escalating up (way up) the management chain, but it was a huge pain and the OSPO decided that the exemption applied only to me, not other Googlers, so of course the moment the company hired someone else who happened to be involved with writing the "Bitcoin Core" software already, they tried to force him to exit the project and the same fight had to happen all over again (with more escalations to top management).

The whole nonsense with someone in middle management (who shall remain nameless) deciding to kill spare time projects because they personally didn't like the idea really turned me off to these clauses. Google doesn't need them, they aren't threatened by side projects of employees and the whole thing causes far, far more drama than it can possibly ever avoid.