Those issues concern me too, and as I've said in another comment somewhere, while it's technically possible to do the same using css, it is actively used via javascripts. I remember reading an article a long time ago about how google's cursor-fingerprinting was able to accurately diagnose parkinson's symptons that were too subtle to detect any other way. And I don't think that google has ever made any attempt to inform such users. That is the character of google. That with their massive powers, they never bother to do good without profit or further control.