Media Queries and Bandwidth
I just read a blog post that stated that media Queries were not a good idea because:
your entire stylesheet, with resources, images, the works - for all viewports - is loaded, before the @media stuff is parsed by the browser.
This isn't entirely true. Although all of the CSS will be downloaded, background-images will not be.
Browsers are smart enough to only load the required assets. To show this I created a very simple sample.