Who should set meeting agendas?

I prefer an Open Space model. When we want optimum engagement, everyone present feels free to invite others into questions that matter to them. We ask who wants to be involved in each of the questions. Those who sign up for each of the questions decides how much time in conversation to spend on each question.

Depending on the time available, in the meeting, we group up as a whole group or in smaller groups to work on the questions that have the greatest functional urgency. We stop a few minutes before the end of the meeting so people can schedule together when unaddressed questions will be worked on by those who signed up for them.

This is obviously the opposite of the disengagement model where one or a select few decide and declare the agenda for the whole group.  In optimum engagement, people feel free to contribute to the questions they have the most interest and strengths for.