Many a time, I recall someone saying, "No one showed up." So the effort to "check the box" was completed and we moved on with what we wanted to do without public input. I believe that social media and specific outreach tools are changing that now--if we really want public input and buy-in. See Collaboration Nation a story in the current edition of Governing Magazine
Perhaps if we were more engaging as agencies and governments there would be more public interest in disaster preparedness. One of the tools mentioned in the article was MindMixer There are others of course that you can pick and choose from--perhaps one right in your own community.
I do think you need to be specific about what you are asking the public to comment on. If you just swing wide the door for comments on anything you are likely to get off-the-wall comments about any number of issues that have no relevance to what it is you want to accomplish.
Like everything else in life--planning the public engagement is important.