I see no reason for the design to 'break' at all really. Images aren't going to resize, we know this, but it can only be as bad as the bg image being too small, or things going onto a few lines instead of one. The issue is can you resize text properly up to a reasonable size and everything still looks ok, yeah? Then fine. If you can increase the text size twice then you did good
Successful text resizing is an accessibility feature (whether done via stylesheet switchers or the browsers own text-resize tools), as long as the content is readable and usability is not compromised then I'm happy. I know usability, design and accessibility are three inseparable elements but I'm not too fussed if my design doesn't quite have the beauty it once did after an increase in text-size. I think my design is compromised after a single text size let alone 3 or 4 (or whatever it goes up to) so quite frankly I don't care. I set the text that size for a reason, it fits with the whole design if someone comes along and resizes the text then fine but in my eyes they might as well have turned off images.
All that matters is that it works, that said if what you say is true then they should take a long hard look at themselves. Design in ems and making a site accessible isn't particularly difficult, making your text resizable is one of the easiest features to add too.
Bad web standards posse, bad!
Pete.
