I think this is actually possible if you use synthetic scrolling (i.e. interpret touch events, compute intertia and use translate3d + requestAnimationFrame). You'd basically have 2 copies of the content area, one blurred w/ css and one not blurred. Render the blurred one above the non blurred one and scroll them in lock step.

You can probably get ok performance if you don't have a lot of images.

A high quality implementation of synthetic scrolling is available at http://github.com/zynga/scroller if you want to play with it.