Reader feedback mechanism
Ballot stuffing or astro-turfing could indeed be used to try to game the "rate this article" mechanism however I believe the appropriate response to this would be making the details of such a votes open and available so that the editors can better analyse such responses and decide how much weight to give - just as editors do to the votes of non-editors on deletion discussions.
Have the "Rate this article" mechanism at the bottom of every page. Include a box as well where people can leave a comment and a reference (automatically added to the talk page). Include a a link (there at the bottom of the page) to the talk page so they can see other peoples comments. Get the useability team to try out alternative formats for this to see what layout gets the most comments and what layout gets the best comments.
Every now and then some one will start a campaign for people to leave comments on one of these pages and we will give those comments appropriate weight. Meanwhile on other pages useful comments will point editors at issues needing attention or good ratings will encourage the work.