This fingerprinting can be defeated by NoScript. Or by turning off JavaScript. A sensible idea would be to make an extension that purges the unique elements from the set they're tracking (i.e. fonts, plugins, mimeTypes, screen size and pixel ratio, etc.) and provide a white-list for sites you want to have that information.

torbutton kills some of it -- they lock your window size to a multiple of some fairly large number of pixels. not sure what else they do....