You weren't asking me, but I'll chime in anyhow. If by "backfire" you mean have I suffered any adverse consequences, then no.
Interestingly, in several cases, I've had other engineers talk to me privately to express gratitude that I said something. They had the same concerns as I, but were too afraid to speak up for fear of consequences.
My attitude has always been that if I'm being punished for doing my job then I'm in the wrong job anyway, so I don't worry about it.