There's variables to deal with such as a Font change for a program may have to global, change defaults within Windows but affects everything. Also involved is the creator/writer/editor of Web pages can use any Font they desire but they have to keep in mind the Font would have to reside within Windows, Linux, Mac OS. Not everyone will have the same exact list of installed Fonts, programs can add in their own and other programs may not be able to use them.
The only program I have installed that has an issue is Microsoft Works 9, pops up a warning that there is more than 500 Fonts installed but otherwise works okay. I keep it running as I used to have clients that had created recipes in it and not many other programs can work with the format.