Adam Morse makes the case against webfonts:
Typography is not about aesthetics, it’s about serving the text. If even a small percentage of people don’t consume your content due to a use of webfonts, your typography is failing.
All this being said I care deeply about aesthetics, and I’ve found the following two sentiments to be true: System fonts can be beautiful. Webfonts are not a requirement for great typography.
I’ve argued in their defense. Also, I reveal a lot of my own biases as a type geek:
I don’t believe that all of human experience can be elegantly communicated via Helvetica, Times, Georgia, or San Francisco. And when I read that “typography is not about aesthetics” then I sigh deeply, heavily and come to the conclusion that 1. yes it is and 2. aesthetics is a problem for the reader. The more ugliness that is pressed upon us, the more lazy we become. Beauty, legibility, subtlety, these are the qualities that are possible with the help of web fonts and without them we are left with a dismal landscape devoid of visual grace or wit.