16:9 is funny looking if you ask me. A few of my friends have Acers with that same ratio... Personally I think if Jobs got handed a 16:9 Macbook case prototype, he would scream out in a horrific fashion that would awaken Jimmy Hoffa from his unknown grave.
16:9 just makes for an overly-long computer case. For a monitor its alright, but a laptop... Everything gets spaced out too wide, if you ask me. Considering how the 27" can cater out with its exemplary video input, I would imagine that like several people have said, its for the black-bar haters who demand 1080p no matter what. On the other hand, a laptop generally will not have 1900x1080 unless its HUGE, ergo the only viable model for a change would be the 17", and I think that the change would piss off more users then the ones that would adopt it.