Hmm... Well, I was thinking of how I could do this myself. You could use the memblock commands to do something... Not really much help though, is it? I'm new to memblocks and not quite sure how to use them...
You could make multiple copies of an object and ghost them. Then position them along a line behind the direction of motion. Have them fade as they get further away from the initial object. This wouldn't really be a blur, but more of a trail. The only way I see of getting a true blur is to use the memblock commands somehow.