Vector Graphics On The Web?

Rob asks: "Bitmaps take up valuable bandwidth and are displayed at different sizes depending on your screen resolution, but Flash animations are big and clunky. Will the increasing take-up of alternative means of browsing (PDAs, mobile phones, TVs, ...) with corresponding variations in screen display and connection speed lead to the emergence of a compact, widely used standard for vector graphics? What are the obstacles which need to be overcome? What vector formats are already in use on the Web?"