It's long been my exprience that one of the classically ineffective ways to groups creative, visionary and productive is asking them if they have any ideas on the topic du jour. I expect little from these outdated exercises in serial opinions and counter-opinions.
New possibilities don't pop out of these kinds of conversations. They come from the very intentional work of cultivating new possibilities. They come from a completely different set of specific questions other than the unproductive: So what do you think?
We ask about what people would love to see possible. We ask people to add value to someone else's possibility. We invite people to articulate their concerns and uncertainties as questions and to take these questions into new learning rather than pointless assumption based debate. We ask people to respond to anything first with what they like about it. This is an explicit process of cultivating possibilities where everyone builds on everything that emerges. It is the very functional opposite of the fairly useless demand for "ideas."