A widescreen aspect ratio doesn't have to be dumb unless the people who design apps and interfaces refuse to make good use of the hardware.
My Windows taskbar has been vertical, running up the right side of my screen, for probably a decade.
One of several reasons that Opera was my web browser of choice for several years was its native support for a vertical tab bar. I could have dozens of tabs open, and be able to see all of them, and read their titles. It was tremendously useful, while it lasted.
PowerPoint has started putting context-sensitive tools and controls on the right side of the screen instead of just at the top, and the slide thumbnails on the left.
Chrome now makes the status bar at the bottom of the window invisible - freeing up an extra line of space in the window - unless it has something important to display (e.g. when you're hovering over a link and want to see the URL).
Reading/comparing/referring to two documents side-by-side is pretty darned useful in a number of different contexts. (Of course then each application window has to have a sensible layout for portrait-oriented display, as well....)
Yes, it's an added burden for developers to have to consider how their application might be used on displays with different aspect ratios. That doesn't mean that they shouldn't do so, and especially not that they should fail to consider how to present their product on the most common format today.