Can you elaborate on what you mean to say here? Is it that PMs have a lot of influence compared to engineers?
With the right top level executive strategy, Product Management can be leveraged for the greater good and keep the company's products fresh and exciting. However, when left to their own devices, they often shift focus towards their own self-interests to the detriment of their company's overall success.
Microsoft is often the most cited example, largely because of how the culture changed after Bill Gates stepped down from the CEO role.
Despite Apple's propaganda otherwise, I get the feeling from some of the things my friends say that the engineers have more sway over product development than Google's do.
foobarqux I hope this answer's your question too.