May be is has to do with that little meaningful word called privacy.
Take out such questions and more will fill it in.
I've followed up with the survey team, and they've assured me that the % revenue question some of you are concerned about is optional. They are also looking into the message some of you are receiving when you click on the survey link.
I understand that some of you are concerned about why we're asking certain questions. I can assure you that the survey team is only interested in aggregate numbers, and it's purely to create the best possible user experience for everyone.
If you don't want to share certain things, you absolutely don't have to, but those of you who do fill out surveys for AdSense are really helping both us and their fellow publishers.