It's a good point, and I've thought about it though. I have a layout which stacks the "bricks" horisontaly for mobile devices. But decided not to use it - because I didn't want to re-build the grid, and break the overlay thing, at that point. I was just finished with my layout - which used 960 grid with fixed width values.
I would say "no" to your question - when I started.
I really didn't care much about mobile users of this particular site. I'm not going to call up businesses and have them have a look at my site - on their mobile phone. And I didn't thought a business would use their phone looking for a webdesigner, or for some marketing materials either, when they sat at their office. That was my thought when I started. But I could be wrong about this, and of course - there's exceptions.
I might reconcider not having a mobile version of my site. But just out of curiosity; Does every site has to be prepared for mobile device?