My experience with agile/scrum is that it puts a more important bounding function on the product/biz side, where they place demands. The most effective scrum meetings I've seen have been where the biz side presents its desires, then the engineers give them actual level of effort, then the biz side decides _right then_ that they didn't care as much about this feature or that. That's an incredible improvement over documents whizzing this way and that, meetings, spreadsheets with LoE. Instead, just a quick meeting of minds.

"I want the blue button very, very badly." "no problem. it will take three of us the entire scrum" "my goodness, I didn't want it that much. Ok, punted."