1280x(anywhere from 720 to 800) is probably the most common resolution for a modern widescreen laptop, and it's very common for Windows users to run with their windows either maximized or manually dragged to take up the entire screen. The ribbon appears to be designed for this, with the option to present a less optimal interface for smaller screens by a combination of resizing interface elements and eliminating uncommonly used ones.

Try resizing the Ribbon all the way from super-wide (if you've got dual monitors, it's particularly interesting) to really narrow. It's quite fun to watch, especially in Office products with zillions of interface controls - the giant buttons and large scrollable boxes full of options become groups of smaller buttons with text, then even smaller buttons without text, then collapse into a single menu, before disappearing altogether into the 'more' button.