Well, nobody has Flash installed anymore (I hope) and I don't believe there is a "modern" way to obtaining a font list (that works on all/majority of browsers). So, at face value, looking at installed fonts doesn't sound like a meaningful attack vector these days.
I believe you can do some stuff with CSS by providing a list of fonts to try and then comparing the size of a block of text, but yes, it is quite a bit harder now.
