Do we really need anonymous surveys? We are all adults, can't we just sit down and talk and sort out issues? If a team is already beyond that point, what is the guarantee that being anonymous will work (assuming it is kept fully anonymous somehow)?
I really wish this were universally true, but many of us deal with the wildly different personalities of our co-workers and bosses. This leaves some uneasy and insecure about sharing even constructive feedback. I don't think surveys are the answer, but for some it is much easier to take those than try to tip-toe around.