When I hover a tag with the mouse, I see the number of followers (i.e. users who added that tag to their favorite tags list) in the popup:
(As far as I know this is the only place where this information is displayed.)
Is there any way to obtain the number of people that ignore a tag?
This number is interesting, e.g., to estimate the popularity of a certain topic or type of question or how useful a tag is (after all, allowing people to ignore certain topics is one of the purposes of tags).