Outside of the question of "is it needed", it'll be interesting to see what happens now that Google has Unveiled WebP, a New Image Format for the Web.
Google explains that of all the bytes transmitted through the intertubes today, 65% is made up of images and photos. In other words, if there's an area where you can save on bandwith - and thus, speed up the web - it's image optimisation. To that end, Google has unveiled WebP, an image format which makes use of the techniques from VP8 video intra frame coding. The container format is lightweight, and based and based on RIFF.
Doesn't most of the people on the web have dsl/cable already now anyway? Is this really needed?