However, unlike many companies, they actually have a process where you can submit your "weekend projects" for Google to review and "gain back" explicit ownership of them.
Basically Google just checks to make sure it's not competing with anything Google's already doing, and then contractually assigns it back to you. (And anecdotally, if it does compete, you may be offered the opportunity to join said team, since it shows you're passionate about it.)
I cannot wait until I'm in a position to work on my own stuff full time.
Disclaimer: works at Google, maintains some FOSS code in my own time, both under my own copyright for some projects and under Google's copyright for others.
This simply doesn't work if you want to be active in a hackerspace or any other community where you iterate on projects quickly.
This depends on the project. If you and the project maintainer are ok with Google maintaining copyright over the code, there's a self-approval process that takes ~2 minutes.
And of course, that's only necessary if I'm working on the side project using company resources. If I'm not, I literally can't do the self-approval. There's only an issue if you want to maintain copyright should you want to monetize your product. Most hobby projects won't encounter those issues.