very well done.... to show motion in a still image you should have part of the object in motion in good focus and you do... an excellent example of how it should look.
My guess and it is just a guess, is that you were panning with the rider???
Yeah, Uctually I take alot of photos for Fiona Taylor, She writes articles for pinkbike. This shot was from the Vancouver Island Cup this year. Heres a link to the most recent article. Most of the shots aren't bad. The first half of the shots I shot in Jpeg LRG Fine, I started Shooting RAW for the ones a little farther down the page. Check it out let me know what you think.