The problem is that high-DPI doesn't mean high bandwidth, and sometimes serving those 3g mobiles with an eye-candy resolution image causes the site to load very

The problem is that high-DPI doesn't mean high bandwidth, and sometimes serving those 3g mobiles with an eye-candy resolution image causes the site to load very slow for them. You will probably want to load low resolution pictures anyway and then if the screen has sufficient DPI load the full resolution afterwards.