Project Managers vs Project Enablers (aka ScrumMasters)
...get in the way.
...tell people what to do.
...tell people what not to do.
...tell people when to do this and when to do that.
Project Enablers (aka ScrumMasters)...
...give people what they need*, get out of the way and let them accomplish their goals.
*what they need: clear goals, a cross-functional team with an embedded QA and someone to ensure everyone is aligned.