If many managers are onboard with an idea, one engineer saying "no" doesn't have much weight. Also, if you keep saying "no" to things, you might be perceived as

If many managers are onboard with an idea, one engineer saying "no" doesn't have much weight. Also, if you keep saying "no" to things, you might be perceived as "negative" and it might come up in performance reviews. And it's often difficult to predict if an idea will work or not - a lot of it comes down to execution and future politics. So, as an engineer, it's probably better to jump on the bandwagon with everyone else, and try to get a promotion from it. It's stupid, but it's how it works. You will not progress within a company by saying "no", even if you are right and it stops a bad project. (I've never worked for google, but did work in a large software corporation)