Referring to the fuseki, a fleet-footed style (ashi ga hayai or ashi-baya in Japanese) aims at rapid development, taking big points, frequently playing tenuki instead of responding locally, and choosing sente lines which permit taking the next big point. Modern fuseki can be characterized as becoming increasingly fleet-footed.
here is fleet-footed development, compared to the more traditional, and slower, move at a. Of course, Black b is now big, but White can either connect or tenuki again, perhaps extending further along the top side.
Bill: How about some better examples from pro commentary?
Fleet-footedness is rarely associated with any negatives, but does involve the risk of becoming thin.