The original Plan 9 file server, kenfs, is a kind of versioning system. He must have thought it was a good idea at the time.

For anyone interested: The Plan 9 File Server by Ken Thompson: http://doc.cat-v.org/plan_9/2nd_edition/papers/fs

(Geoff Collyer later added 64bit support: http://doc.cat-v.org/plan_9/2nd_edition/papers/fs and eventually Bell Labs replaced kenfs with Fossil: http://doc.cat-v.org/plan_9/4th_edition/papers/fossil/ although some members of the Plan 9 community still prefer the simplicity of kenfs)

I wouldn't take it that way. It's more that it would be insane to work on shared code with thousands of engineers without version control. At Bell there were far fewer programmers, so keeping track of changes would be much more straightforward.

I agree that version control is nearly essential. But Ken's phrasing was not "Well of course I use SCM for everything." it's "Google is making me." The way he said it, even in jest, suggests a bit of resentment and a feeling that it's not something he feels is best for this project for some reason.