[saalweachter]

It also shouldn't be in websites. This would make an awesome browser plug-in, which would also let you calibrate it (as mentioned by someone else) to be the "right size" for your vision.

I think a U-shaped curve could also be good: big text when you're far away, small text when you're at normal viewing distances, and zoom further [esp for full-page zoom] when you lean in very close.