This article from Wired/WebMonkey sums it up nicely… well, maybe not nicely…
The web needs a more intelligent way to serve images.
No one wants to waste bandwidth sending large images over limited mobile pipes, but everyone wants images to look good on the myriad screens connecting to today’s web. Currently web authors use a variety of hacks to (incompletely) work around this problem, but to really solve it the web likely needs new tools.
Unfortunately, thanks to miscommunication between standards bodies, web developers and browser makers, instead of a solution to the image problem what developers got this week feels more like a slap in the face. Eventually an adaptive image solution will likely emerge, but the real lesson for many developers will be about how the standards process works and how they fit into it, if at all.