As a web designer, I despair of users upping the font size and screwing up the words-per-line. Which is why I like Safari's iOS-like pinch-zoom feature. I do wish all browsers would move in that direction and in the end disallow users to arbitrarily up font sizes.
That said, crazygringo's point is valid insofar as people do up their font sizes as a matter of course.
That said, crazygringo's point is valid insofar as people do up their font sizes as a matter of course.