I definitely agree, but that's true of any system. The particulars of the pitfalls may vary, but a good system can't overpower bad management. We mitigate the stakeholder issue by having BAs that act as the liason between devs and stakeholders, knowing just enough about the dev side to manage expectations while helping to prioritize the things stakeholders want most. Our stakes are also, mercifully, pretty aware that they don't always know what will be complex and what will be trivial, so they accept the effort we assign to items.