On a related note, I really like writing/reading the age 18-24 range--basically, college age--because a lot is changing in life then, as compared to high school. That's the true "young adult," if you ask me, and I'd call the high school stuff "teen lit." But it's far too late to change the industry terminology now. Some people have called books about the college age "new adult," and I've seen it applied to my books of that category (RELATIVELY HONEST and WHAT SCOTLAND TAUGHT ME), but introducing that distinction is splitting more instead of lumping more, so I don't think it's necessary.
Thanks to modmerseygirl for pointing me to that article and getting me rambling about it.