[Animats]

Flash had an scheduled loading scheme, so the timeline specified when an asset would be sent as you played a Flash animation. Macromedia had authoring tools which would try to slot the assets in the timeline so they'd be available when needed, while staying under a bandwidth limit.

You could, in theory, do that with WebGL. Google is all fired up about "preloading" lately. This is an authoring tool problem, and if WebGL games get serious, there will probably be author-side tools for this.