Could've been worse. I have a boss who secretly hates a few employees. When he gets negative anonymous feedback, he'll automatically imagine these were the guys who wrote them.
The charismatic ones can write the boss to hell, but he will never suspect a thing.
Anonymous feedback that involves short written responses is pure evil. It induces paranoia.
At Microsoft, we solve poor anonymous surveys two ways: (a) by firing the guys that are whining - we don't need negativists and they clearly have issues (b) by not sending surveys to everyone.
Surveys are anonymous but of course it needs your domain credentials, ip, mac address, latitude, longitude and your Windows Live Id, just so you can't complete the survey twice.
Surveys used to be big until two years back when they figured they had to fix most of the responses by !$%*!$%* outliers and cook the results.