Attendance in public meetings is low and highly selective Although citizens express their intention to participate in public  engagement activities, in real world, they are less likely to show up.  Low turnout rate in public meetings can lead serious sampling biases  when attendees and non-attendees significantly differ in their  interests. For example, attendees can be more interested in politics and  involved in more personal discourses than non-attendees. In this case,  their opinions can be slanted to one side. 

Group dynamics and personality traits of participants Depending the makeup of participants, group dynamics and personality  characteristics of participants can considerably affect the outcomes of  discussions. A small number of outspoken participants can make more than  half of the comments during the discussions while least outspoken  members make a very small portion of the comments.

Moderated/controlled settings of public meetings In order to  minimize the potential effects of participants demographic and  cognitive characteristics on conversations, public meetings or consensus  conferences tend to be carefully moderated and guided by facilitators.  In such artificial setting, participants may behave in different ways  that may differ from what is likely to occur in real-world discussions 

Spillovers from public meetings to real-world discussion The social implication effect of follow-up media coverage of public  meetings or other engaging events may help transfer issues from these  small group discussions to the broader community. However, in the case  of the U.S., a spillover effect from public meetings into media  discourse are minimal at best.

Knowledge gap issues Public meetings and consensus conferences may create knowledge gaps  between  participants. The demographic,  and cognitive differences between two groups in public  meeting may lead to differing outcomes of public engagement. For  example, highly educated participants may learn more from discussions  and dominate the conversation while less educated members listen to  their arguments. Furthermore, only small proportions of the population  who may be already informed attend public meetings while the majority of  the population who may need information the most do not. In such case,  any public engagement effort may widen existing gaps further. 

  Groups that already had influence were often the only ones consulted

People who did not have the resources to find out would usually not  be able to be part of a consultation, even if the decision it was meant  to influence might have a major impact on them.

There were no agreed safeguards against consultations being used  cynically by decision-makers to make it look like they had sought to  canvass other opinions, while in fact having set a new policy in place  even before it asked the question