[throwaways885]

I don't think things have changed that much, only Google grew so big that 20% projects became a potential damper on your career (the incentives of perf and promo and all that horrible stuff). But the freedom has always technically been there.

[oakfr]

I am a tech lead and find it surprising that 20% projects could damper your career, perf & promo etc. Where I work, a well-executed 20% project is seen as very positive during the perf review. In fact, doing zero 20% projects for a long period of time could actually damper your career.

[OJFord]

But if nothing came of the 20% work, you could've done 25% more on the core job, doing positive performance things there. I'm pretty sure that's what's meant about it being a career dampener, not that it wouldn't be great to hit on something fantastic and accepted as a new core product with thousands working on it full-time. (IANAG.)

[oakfr]

Everything is obvious in the hindsight. 20% projects carry a risk, failing one or more 20% is fine. Failing many is seen as lack of judgment and does dampen your career eventually. My point was that, with reasonable judgment, an engineer can get good stuff done with a 20% project. Also, not every 20% project needs to become a fantastic new core product to be considered a success.

[pushrax]

Sounds very plausible from the outside.

Also implies a widely varying experience with the program; levels of promotion politics must vary across the company, and levels of recognition for anyone's particular project must also vary.