and certainly not for mobile devices. the size of a device determines its mobility: those intended to be mobile, such as laptops and smartphones, should be small, small, small.
laptop manufacturers might consider that some people still use their laptops for things other than movie-watching, and that some people enjoy carrying around a laptop that is fast and fully functional but not the size of a butcher block cutting board. for those who don't watch movies on their laptops, a 16:9 screen proves mildly useful for using the kind of application that has toolbars on the side, but is worse than useless for popular laptop use-cases such as document-reading, code-writing, and scrolling-page navigation. a 4:3, retina-display, 11" macbook air would be a dream with a small footprint. it is all but certain that 2 out of the 3 will be in the next air refresh; will the 4:3 aspect ratio be an option? we, or at least i, can only hope.
smartphones are inherently mobile devices, and the good ones (fast, high-resolution, with good platform compatibility) are now almost all too big. the few small phones these days are mostly underpowered budget models with crummy displays. the iphone is the only exception to this trend: a premium phone with a small footprint. samsung's galaxy line would be more competitive with the iphone if they released a galaxy nexus with a better designed rear camera housing and a smaller footprint than the iphone.
though i am not an apple fanboy, i will say this: apple gets a lot of credit for detail-oriented hardware but they should get more credit for resisting—as few major hardware manufacturers appear to be doing—the urge to differentiate their products by simply making them bigger. that, as kierkegaard says, is the bad infinite.