Hi Dana,
Unfortunately you are correct with your assumption that it is impossible to eliminate all bad press from rating sites online. The good news is you can always reduce the bad press, by simply providing quality service to your clients. Of course, you will always have that one client that will not be happy no matter what you do, but as long as you know you did everything in your power to address their issue, than that alone will limit what that client can say about your service.
One thing that really works on my sites with regards to Ratings sites is our policy for our leasing and management staff to monitor the sites on a daily basis. Each site is to respond to all posting negative or positive, either thanking them for a good note or simply addressing the issue without an online dispute. The staff is not allowed to identify themselves as residents or client, but actually identify themselves as employees of the community. This way, current and potential clients will see that the staff is actually involved and that they care about their clients and the wellbeing of their community.
Furthermore, I would suggest you have what is call an online station in your community room or leasing center, where you can direct happy clients to post something online while visiting you. This way, they have the convenience of posting a response right there and then, rather than go home and possibly forget to post their wonderful experience. Also, during your resident events, you can make it into a contest or an activity to post their great experience online.
Hope this helps! Good luck
Sincerely,
Pedro