I'd just assumed that when Apple introduced that crazy-thin 12" MacBook a couple years ago, it was meant to replace both product lines. I don't understand why it's necessary to maintain a third discrete product line. Why not add a 13" variant to the standard MacBook line with i5 and i7 processor choices? That would be similar to what they do with the MacBook Pro line.
Is there some other difference that I'm overlooking?