[throwawayGogEng]

> If the build breaks for an unrelated reason, you can lose a whole week of development to screwing around.

This happens often on some projects at Google (although 2 days is the longest I've seen it broken). Others have told me they use this time for documenting code and writing design-documents.

> When working in that kind of environment, I tend to maintain my own VCS, then squash my commits when integrating with the main VCS.

Google actually has a tool that allows developers to use Git on their local machine, which is squashed into a CL when pushed. However, some projects are too reliant on the old system for this to work.