My most successful teaching moments have always included an open-ended question that required collaboration (especially student-teacher-community) to explore and develop an answer. Professional development for educators should work the same way. If teachers (acting as students) brought their questions to a forum made up of other teachers (acting as teachers in a teacher community), real solutions could arise.
In my district, the best professional development currently occurs in the hallways of my building when teachers literally bump into each other and say things like "Hey, I've got this kid. . ." or "I had this idea for a lesson. . . ." These 5 minutes we have between classes is where the best ideas are born through two teachers exploring solutions to a real problem.