I believe that professional development (PD) is most effective when teachers have a clear understanding of the larger issues: What's at stake? Administrators (building, district or county) often make the mistake of not cultivating teachers' shared understanding of the larger issues. Teachers therefore do not see how the PD is linked to student engagement, personal growth, or pedagogical concept development.
I recently received an email indicating that district administrators were going to "...do professional development to teachers." What am I, a bowling ball?!?