If you know you can check before voting, but for new users this might not be the case. I'd recommend to anyone creating a poll that they probably should mention if they are making it public or private. Some issues like DRM, copyright, filesharing, or forum related issues might not feel comfortable with their votes known.
And no worries, no poll starter or mod/admin tries to deceive anyone to 'out' them, it is simply a feature of the forum software.
-MJ