• DOPs involve a large number of participants (between 250 and 600), therefore set-up costs are high.
• Informing the participants normally irequires access to experts in a number of fields of knowledge
• Speakers need to be organised
• With so many participants' opinions, managing data is a significant undertaking.
• Organising and running the event can be time consuming.
• Organisers need to allow time to select participants, undertake an initial opinion poll, allow two-four days for the deliberation process, and then allow time for another poll, and formulating the report.