I find here in the valley companies value engineers who want a say in product direction. So we have companies filled with engineers who don't want to just be shoved a task and relegated to coding monkey status. I think that's where most of the ambiguity exists.

As I see it, a PM should be your team's CEO and the lead engineer should be the CTO. Together the pair of you are delivering on a single vision, one person outwardly and the other inwardly. Yet for the magic to work, the entire team needs to be on the same page. No one person should be setting the goals for everyone else. Simple put, the PM isn't the engineers bitch and engineering is the PM's bitch.