I thought that perhaps, for a trial period, we could add a
prominently-placed button in articles for not-logged-in readers with
the title of "Report an Error or Suggest Information to Add".
Since so many people don't realise that Wikipedia is for anybody to
edit, this could take them to a new page that explained in bold
letters the concept of Wikipedia and that they could edit the article
themselves, but still have an error-report field in case they still
didn't get it.
While this would obviously be open to abuse, it might also provide
useful feedback from people who otherwise wouldn't contribute
anything, and would definitely serve to let these people know that the
power is in their hands, what with the boldly-placed notice that THEY
can fix it themselves and all.
I'm sure there would be way too much feedback to ever completely sift
through, but I still think it might be useful.
Mark